Movable body drive method, movable body drive system, pattern formation method, pattern forming apparatus, exposure method, exposure apparatus, and device manufacturing method

ABSTRACT

Positional information of a movable body in a Y-axis direction is measured using an interferometer and an encoder whose short-term stability of measurement values excels when compared with the interferometer, and based on the measurement results, a predetermined calibration operation for obtaining correction information for correcting measurement values of the encoder is performed. Accordingly, by using measurement values of the interferometer, correction information for correcting the measurement values of the encoder whose short-term stability of the measurement values excels the interferometer is obtained. Then, based on the measurement values of the encoder and the correction information, the movable body is driven in the Y-axis direction with good precision.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a division of U.S. patent application Ser. No. 15/211,669 filedJul. 15, 2016, which in turn is a division of U.S. patent applicationSer. No. 13/007,503 filed Jan. 14, 2011 (now U.S. Pat. No. 9,423,703),which in turn is a division of U.S. patent application Ser. No.12/900,372 filed Oct. 7, 2010 (now U.S. Pat. No. 9,423,702), which is adivision of U.S. patent application Ser. No. 11/655,082 filed Jan. 19,2007 (now U.S. Pat. No. 7,839,485) and which claims the benefit ofProvisional Application No. 60/851,045 filed Oct. 12, 2006. Thedisclosure of each of the prior applications is hereby incorporatedherein by reference in its entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to movable body drive methods, movablebody drive systems, pattern forming methods, pattern forming units,exposure methods, exposure apparatus, and device manufacturing methods,and more particularly to a movable body drive method in which a movablebody is driven in at least a uniaxial direction, a movable body drivesystem suitable for applying the method, a pattern formation method thatuses the movable body drive method, a pattern forming apparatus that isequipped with the movable body drive system, an exposure method thatuses the movable body drive method, an exposure apparatus that has themovable body drive system, and a device manufacturing method that usesthe pattern forming method.

Description of the Background Art

Conventionally, in a lithography process for manufacturing microdevices(electronic devices and the like) such as a liquid crystal displayelement or the like, a reduction projection exposure apparatus by astep-and-repeat method (the so-called stepper), a scanning projectionexposure apparatus by a step-and-scan method (the so-called scanningstepper (also called a scanner)) and the like have been relativelyfrequently used.

With these types of exposure apparatus, in order to transfer a patternof a reticle (or a mask) onto a plurality of shot areas on a wafer, thewafer stage that holds the wafer is driven in a XY two-dimensionaldirection by a linear motor or the like. Especially in the case of ascanning stepper, not only the wafer stage but also the reticle stage isdriven in the scanning direction with predetermined strokes by a linearmotor or the like. Position measurement of the reticle stage and thewafer stage is normally performed using a laser interferometer, whichhas good stability of measurement values over a long period of time, andalso has high resolution.

However, due to finer patterns that come with higher integration ofsemiconductor devices, position control of the stages with higherprecision is becoming required, and short-term fluctuation ofmeasurement values due to temperature fluctuation of the atmosphere onthe beam optical path of the laser interferometer is now becoming amatter that cannot be ignored.

Meanwhile, recently, as a type of a position measurement unit, anencoder that has a measurement resolution of the same level or higherthan a laser interferometer has been introduced (refer to, for example,U.S. Pat. No. 6,639,686). However, since the encoder uses a scale(grating), various error factors (drift of grating pitch, fixed positiondrift, thermal expansion and the like) that occur in the scale due tothe passage of use time exist, which makes the encoder lack inmechanical long-term stability. Therefore, the encoder has a drawback oflacking measurement value linearity and being inferior in long-termstability when compared with the laser interferometer.

SUMMARY OF THE INVENTION

The present invention has been made in consideration of thecircumstances described above, and according to the first aspect of thepresent invention, there is provided a first movable body drive methodin which a movable body is driven in at least a uniaxial direction, themethod comprising: a first process in which a calibration operation isperformed where positional information of the movable body in theuniaxial direction is measured using a first measurement unit and asecond measurement unit whose measurement values excel in short-termstability when compared with measurement values of the first measurementunit, and based on measurement results of the first and secondmeasurement units, correction information for correcting measurementvalues of the second measurement unit is decided; and a second processin which the movable body is driven in the uniaxial direction based onthe measurement values of the second measurement unit and the correctioninformation.

According to this method, by the calibration method above, correctioninformation is decided for correcting the measurement values of thesecond measurement unit whose short-term stability of the measurementvalues excel when compared with the measurement values of the firstmeasurement unit, using the measurement values of the first measurementunit. Then, based on the measurement values of the second measurementunit and the correction information, the movable body is driven in theuniaxial direction. Accordingly, it becomes possible to drive themovable body in the uniaxial direction with good accuracy, based on themeasurement values of the second measurement unit that have beencorrected using the correction information, that is, the measurementvalues of positional information of the movable body in the uniaxialdirection whose long-term stability is also favorable, in addition tothe short-term stability.

According to the second aspect of the present invention, there isprovided a second movable body drive method in which a movable body isdriven within a two-dimensional plane parallel to a first axis and asecond axis orthogonal to each other wherein positional information ofthe movable body in a direction parallel to the first axis is measured,using a pair of first gratings that each include a grating periodicallydisposed in a direction parallel to the first axis within a planeparallel to the two-dimensional plane on the movable body and is placedapart in a direction orthogonal to the longitudinal direction of thegrating within the plane and a first encoder that has a head unit thatintersects the longitudinal direction, and positional information of themovable body in a direction parallel to the second axis is measured,using a second grating that includes a grating, which extends in adirection intersecting the longitudinal direction of the first gratingserving as a longitudinal direction and is periodically disposed in adirection parallel to the second axis, and a second encoder that has ahead unit that intersects the longitudinal direction of the secondgrating, whereby the movable body is driven based on the positionalinformation that has been measured.

According to this method, as long as the movable body remains within apredetermined stroke range where a head unit that the first encoder hasfaces at least one of the gratings of the pair of the first gratings,and a head that the second encoder has faces the second grating, then,at least one of the first grating and the first encoder measure thepositional information of the movable body in the direction parallel tothe first axis, and the second grating and the second encoder measurethe positional information of the movable body in the direction parallelto the second axis. Since the short-term stability of the measurementvalues of the first and second encoders is favorable, the positionalinformation of the movable body within the two-dimensional plane ismeasured with good accuracy. Then, the movable body is driven, based onthe positional information of the movable body measured with goodaccuracy. Accordingly, it becomes possible to drive the movable bodywith good accuracy.

According to the third aspect of the present invention, there isprovided a third movable body drive method in which a movable body isdriven at least in a uniaxial direction, the method comprising: a driveprocess in which based on measurement values of an encoder thatirradiates a detection light on a grating placed on an upper surface ofthe movable body with a predetermined direction serving as a perioddirection and measures positional information of the movable body in thepredetermined direction based on its reflection light and correctioninformation of a pitch of the grating, the movable body is driven in thepredetermined direction.

According to this method, the movable body can be driven with goodaccuracy without being affected by drift or the like of the gratingpitch.

According to the fourth aspect of the present invention, there isprovided a first pattern formation method in which a pattern is formedon an object, wherein a movable body on which the object is mounted isdriven using one of the first and third movable body drive method of thepresent invention so that pattern formation with respect to the objectcan be performed.

According to this method, by performing pattern formation on the objectmounted on the movable body driven with good accuracy using one of thefirst and third movable body drive method, it becomes possible to formthe pattern on the object with good accuracy.

According to the fifth aspect of the present invention, there isprovided a second pattern formation method in which a pattern is formedon an object, wherein at least one of a plurality of movable bodiesincluding a movable body on which the object is mounted is driven usingone of the first and third movable body drive method of the presentinvention so that pattern formation with respect to the object can beperformed.

According to this method, for pattern formation with respect to theobject, at least one of a plurality of movable bodies is driven withgood accuracy by one of the first and third movable body drive method,and a pattern is generated on the object mounted on one of the movablebodies.

According to the sixth aspect of the present invention, there isprovided a device manufacturing method including a pattern formationprocess wherein in the pattern formation process, a pattern is formed ona substrate using one of the first and second pattern formation methodof the present invention.

According to the seventh aspect of the present invention, there isprovided a first exposure method in which a pattern is formed on anobject by irradiating an energy beam, wherein a movable body on whichthe object is mounted is driven using one of the first and third movablebody drive method of the present invention so that the energy beam andthe object are relatively moved.

According to this method, for the relative movement of the energy beamirradiated on the object and the object, the movable body on which theobject is mounted is driven with good accuracy using one of the firstand third movable body drive method of the present invention.Accordingly, it becomes possible to form a pattern on an object withgood accuracy by scanning exposure.

According to the eighth aspect of the present invention, there isprovided a first movable body drive system that drives a movable body inat least a uniaxial direction, the system comprising: a firstmeasurement unit that measures positional information of the movablebody in the uniaxial direction; a second measurement unit that measurespositional information of the movable body in the uniaxial directionwhose short-term stability of measurement values excels the firstmeasurement unit; a calibration unit that performs a calibrationoperation of deciding correction information so as to correctmeasurement values of the second measurement unit using the measurementvalues of the first measurement unit; and a drive unit that drive themovable body in the uniaxial direction based on the measurement valuesof the second measurement unit and the correction information.

According to this system, the calibration unit performs the calibrationoperation described above, and correction information is decided forcorrecting the measurement values of the second measurement unit whoseshort-term stability of the measurement values excels when compared withthe first measurement unit, using the measurement values of the firstmeasurement unit. Then, based on the measurement values of the secondmeasurement unit and the correction information, the movable body isdriven in the uniaxial direction. Accordingly, it becomes possible todrive the movable body in the uniaxial direction with good accuracy,based on the measurement values of the second measurement unit that havebeen corrected using the correction information, that is, themeasurement values of positional information of the movable body in theuniaxial direction whose long-term stability is also favorable, inaddition to the short-term stability.

According to the ninth aspect of the present invention, there isprovided a second movable body drive system that drives a movable bodywithin a two-dimensional plane parallel to a first axis and a secondaxis which are orthogonal, the system comprising: a first grating placedon a plane parallel to the two-dimensional plane on the movable bodythat also includes a grating disposed periodically in a directionparallel to the first axis; a pair of second gratings that extends in adirection intersecting the direction serving as a longitudinal directionon a plane parallel to the two-dimensional plane on the movable body,and is also placed apart in a direction orthogonal to the longitudinaldirection, and also includes a grating periodically disposed in adirection parallel to the second axis; a first encoder that has a headunit intersecting the longitudinal direction of the first grating, andmeasures positional information of the movable body in the directionparallel to the first axis along with the first grating; a secondencoder that has a head unit intersecting the longitudinal direction ofthe pair of second gratings, and measures positional information of themovable body in the direction parallel to the second axis along with thepair of second gratings; and a drive unit that drives the movable bodybased on positional information measured by the first and secondencoders.

According to this method, as long as the movable body remains within apredetermined stroke range where a head unit that the first encoder hasfaces at least one of the gratings of the pair of the first gratings,and a head that the second encoder has faces the second grating, then,the first grating and the first encoder measure the positionalinformation of the movable body in the direction parallel to the firstaxis, and the second grating and the second encoder measures thepositional information of the movable body in the direction parallel tothe second axis. Since the short-term stability of the measurementvalues of the first and second encoders is favorable, the positionalinformation of the movable body within the two-dimensional plane ismeasured with good accuracy. Then, the movable body is driven, based onthe positional information of the movable body measured with goodaccuracy. Accordingly, it becomes possible to drive the movable bodywith good accuracy.

According to the tenth aspect of the present invention, there isprovided a third movable body drive system that drives a movable bodywithin a two-dimensional plane parallel to a first axis and a secondaxis which are orthogonal, the system comprising: a first grating thatextends in a direction parallel to the second axis with the directionserving as a longitudinal direction on the movable body, and also has agrating periodically disposed in a direction parallel to the first axis;a second grating that extends in a direction parallel to the first axiswith the direction serving as a longitudinal direction on the movablebody, and also has a grating periodically disposed in a directionparallel to the second axis; a first encoder that has a head unit thatintersects the direction parallel to the second axis and measurespositional information of the movable body in the direction parallel tothe first axis along with the first grating; a second encoder that has ahead unit that intersects the direction parallel to the first axis andmeasures positional information of the movable body in the directionparallel to the second axis along with the second grating; and a driveunit that drives the movable body based on the positional informationmeasured by the first and second encoders, wherein at least one of thefirst and second encoders has a plurality of the head units placed apartin the longitudinal direction.

According to this system, by the first grating and the first encoder,and the second grating and the second encoder, rotation (rotation aroundthe axis orthogonal to the two-dimensional plane) in the two-dimensionalplane is measured, in addition to the positional information of themovable body in the direction parallel to the first axis and thepositional information in the direction parallel to the second axis.Further, since the short-term stability of the measurement values of thefirst and second encoders is favorable, positional information(including rotational information) of the movable body within thetwo-dimensional plane is measured with good accuracy. The, based on thepositional information of the movable body measured with good accuracy,the drive unit drives the movable body. Accordingly, it becomes possibleto drive the movable body with good accuracy.

According to the eleventh aspect of the present invention, there isprovided a fourth movable body drive system that drives a movable bodyin at least uniaxial direction, the system comprising: an encoder thatirradiates a detection light on a grating placed in a predetermineddirection, which serves as a periodical direction, on an upper surfaceof the movable body and measures positional information of the movablebody in the predetermined direction based on a reflection light; and adrive unit that drives the movable body in the predetermined directionbased on measurement values of the encoder and correction information ofa pitch of the grating.

According to this system, the drive unit drives the movable body in thepredetermined direction, based on the measurement values of the encoderand the correction information of the pitch of grating. Accordingly, themovable body can be driven with good accuracy without being affected bydrift or the like of the grating pitch.

According to the twelfth aspect of the present invention, there isprovided a first pattern forming apparatus that forms a pattern on anobject, the unit comprising: a patterning unit that generates a patternon the object; and any one of the first to fourth movable body drivesystem of the present invention, wherein the movable body drive systemdrives the movable body on which the object is mounted so as to performpattern formation with respect to the object.

According to this system, by generating a pattern with the patterningunit on the object on the movable body driven with good accuracy usingany one of the first to fourth movable body drive system of the presentinvention, it becomes possible to form a pattern on an object with goodaccuracy.

According to the thirteenth aspect of the present invention, there isprovided a second pattern forming apparatus that forms a pattern on anobject, the unit comprising: a patterning unit that generates a patternon the object; a plurality of movable bodies including a movable body onwhich the object is mounted; and any one of the first to fourth movablebody drive system of the present invention, wherein the movable bodydrive system drives at least one of the plurality of movable bodies soas to perform pattern formation with respect to the object.

According to this system, for pattern formation with respect to theobject, at least one of a plurality of movable bodies is driven withgood accuracy by one of the first to fourth movable body drive system,and the patterning unit generates a pattern on the object mounted on oneof the movable bodies.

According to the fourteenth aspect of the present invention, there isprovided a first exposure apparatus that forms a pattern on an object byirradiating an energy beam, the apparatus comprising: a patterning unitthat irradiates the energy beam on the object; and any one of the firstto fourth movable body drive system of the present invention, whereinthe movable body on which the object is mounted is driven by the movablebody drive system so that the energy beam and the object are relativelymoved.

According to this apparatus, for relative movement of the energy beamirradiated on the object from the patterning unit and the object, themovable body on which the object is mounted is driven with good accuracyusing any one of the first to fourth movable body drive system of thepresent invention. Accordingly, it becomes possible to form a pattern onan object with good accuracy by scanning exposure.

According to the fifteenth aspect of the present invention, there isprovided a second exposure method in which an exposure operation by astep-and-scan method that alternately repeats scanning exposure ofsynchronously moving a mask and an object in a predetermined scanningdirection so as to transfer a pattern formed on the mask onto a dividedarea on the object and movement of the object to perform scanningexposure on a following divided area is performed to sequentiallytransfer the pattern onto a plurality of divided areas on the object,wherein positional information of a mask stage that holds the mask ismeasured with an encoder and movement of the mask stage is controlled,based on measurement values of the encoder and correction information ofthe measurement values of the encoder decided from positionalinformation of the mask stage using the encoder and an interferometer atleast during scanning exposure to each divided area, and the correctioninformation is calibrated, based on measurement values of theinterferometer and the encoder stored during the exposure operation bythe step-and-scan method.

According to this method, on exposure by the step-and-scan method to thenext object, the movement of the mask stage during scanning exposure (atthe time of pattern transfer) of each divided area can be controlledwith good accuracy, based on the measurement values of the encoder whichhave been corrected using the correction information, that is,measurement values of the positional information of the mask stage inthe scanning direction having good linearity and long-term stability, inaddition to good short-term stability. Accordingly, the pattern formedon the mask can be transferred onto the plurality of divided areas onthe object by scanning exposure with good precision.

According to the sixteenth aspect of the present invention, there isprovided a second exposure apparatus that performs an exposure operationby a step-and-scan method which alternately repeats scanning exposure ofsynchronously moving a mask and an object in a predetermined scanningdirection so as to transfer a pattern formed on the mask onto a dividedarea on the object and movement of the object to perform scanningexposure on a following divided area, the apparatus comprising: a maskstage movable in at least the scanning direction holding the mask; anobject stage movable in at least the scanning direction holding theobject; an interferometer and an encoder that measure positionalinformation of the mask stage in the scanning direction; and a controlunit that controls movement of the mask stage, based on measurementvalues of the encoder and correction information of the measurementvalues of the encoder decided from positional information of the maskstage using the encoder and an interferometer at least during scanningexposure to each divided area, and calibrates the correctioninformation, based on measurement values of the interferometer and theencoder stored during the exposure operation by the step-and-scanmethod.

According to this apparatus, when the controller performs the exposureoperation by the step-and-scan method in which a pattern is sequentiallytransferred onto a plurality of divided areas on an object, thecontroller controls the movement of the mask stage based on themeasurement values of the encoder and the correction information of themeasurement values of the encoder decided from the positionalinformation of the mask stage by the encoder and the interferometerduring the scanning exposure of each divided area, and calibrates thecorrection information based on the measurement values of theinterferometer and the encoder stored during the exposure operation bythe step-and-scan method. Accordingly, the movement of the mask stageduring scanning exposure (at the time of pattern transfer) with respectto each divided area on the object after calibration can be controlledwith good precision, based on the measurement values of the encoder thathave been corrected using the calibrated correction information, thatis, measurement values of the positional information of the mask stagein the scanning direction having good linearity and long-term stability,in addition to good short-term stability. Accordingly, the patternformed on the mask can be transferred with good accuracy onto theplurality of divided areas on the object by the scanning exposure.

According to the seventeenth aspect of the present invention, there isprovided a third exposure apparatus that synchronously moves a mask andan object in predetermined scanning direction with respect to anillumination light and transfers a pattern formed on the mask onto theobject, the apparatus comprising: a mask stage movable in at least thescanning direction holding the mask; an object stage movable in at leastthe scanning direction holding the object; an interferometer and anencoder that measure positional information of the mask stage in thescanning direction; a calibration unit that decides correctioninformation in which measurement values of the encoder is correctedusing measurement values of the interferometer, based on measurementresults of the interferometer and the encoder, which are measured bydriving the mask stage in the scanning direction at a slow speed at alevel in which the short-term variation of the measurement values of theinterferometer can be ignored and measuring positional information ofthe mask stage in the scanning direction using the interferometer andthe encoder; and a control unit that controls movement of the mask stageduring transfer of the pattern, based on the measurement value of theencoder and the correction information.

According to this apparatus, by the calibration unit, the mask stage isdriven in the scanning direction at a slow speed at a level in which theshort-term variation of the measurement values of the interferometer canbe ignored, and the positional information of the mask stage in thescanning direction is measured using the interferometer and the encoder.Then, based on the measurement results of the interferometer and theencoder, correction information for correcting the measurement values ofthe encoder using the measurement values of the interferometer, that is,correction information for correcting the measurement values of theencoder whose short-term stability of the measurement values excels theinterferometer, using the measurement values of the interferometer whoselinearity and long-term stability of the measurement values excels theencoder, is decided. Then, the control unit controls the movement of themask stage during pattern transfer, based on the measurement values ofthe encoder and the correction information. Accordingly, it becomespossible to control the movement of the mask stage in the scanningdirection during pattern transfer with good accuracy, based on themeasurement values of the encoder that has been corrected using thecorrection information, that is, the measurement values of thepositional information of the mask stage having good linearity andlong-term stability, in addition to good short-term stability.Accordingly, the pattern formed on the mask can be transferred with goodaccuracy onto the object by the scanning exposure.

According to the eighteenth aspect of the present invention, there isprovided a fourth exposure apparatus that synchronously moves a mask andan object in predetermined scanning direction with respect to anillumination light and transfers a pattern formed on the mask onto theobject, the apparatus comprising: a mask stage movable in at least thescanning direction holding the mask; an object stage movable in at leastthe scanning direction holding the object; an interferometer and anencoder that measure positional information of the mask stage in thescanning direction; a calibration unit that corrects scaling error in amap information that denotes a relation between the measurement valuesof the interferometer and the measurement values of the encoder, basedon the measurement values of the interferometer and the encoder eachobtained at a predetermined sampling interval, while position settingthe mask stage at a plurality of positions including a first positionand a second position which are positions on both edges of a range wherethe illumination light is irradiated on a pattern area of a mask subjectto exposure; and a control unit that controls the movement of the maskstage during transfer of the pattern, based on the measurement values ofthe encoder and the map information after correction.

According to this apparatus, the calibration unit obtains measurementvalues of the interferometer and the encoder at a predetermined samplinginterval while position setting the mask stage at a plurality ofpositions including a first position and a second position which arepositions on both edges of a range where the illumination light isirradiated on a pattern area of a mask subject to exposure, and based onthe measurement values that have been obtained, the calibration unitperforms calibration operation of correcting scaling error in a mapinformation that denotes a relation between the measurement values ofthe interferometer and the measurement values of the encoder. That is,the scaling error of the map information that denotes a relation betweenthe measurement values of the encoder whose short-term stability of themeasurement values excels the interferometer and the measurement valuesof the interferometer whose linearity and long-term stability of themeasurement values excels the encoder is corrected. Then, by the controlunit, based on the measurement values of the encoder and the mapinformation after correction, the movement of the mask stage duringpattern transfer is controlled. Accordingly, it becomes possible tocontrol the movement of the mask stage in the scanning direction duringpattern transfer with good accuracy, based on the map information aftercorrection and the measurement values of the encoder.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a view that shows a schematic arrangement of an exposureapparatus related to an embodiment;

FIG. 2 is a planar view that shows a reticle stage, along with anencoder system which measures positional information of the reticlestage and an interferometer system;

FIG. 3 is a planar view that shows a wafer stage, along with an encoderwhich measures positional information of the wafer stage and aninterferometer;

FIG. 4 is an extracted view that shows a Y interferometer which measuresa position of wafer stage WST in FIG. 1, a Z interferometer, and theneighboring components;

FIG. 5 is a view that shows an example of an arrangement of an encoder;

FIG. 6 is a block diagram of a control system partially omitted, relatedto stage control of an exposure apparatus related to an embodiment;

FIG. 7 is a view (No. 1) for describing a switching operation of aposition measurement system;

FIG. 8 is a view (No. 2) for describing a switching operation of aposition measurement system;

FIG. 9 is a view (No. 1) for describing a scanning operation of areticle stage for exposure including a switching (linking themeasurement values) operation of an encoder on the reticle side;

FIG. 10 is a view (No. 2) for describing a scanning operation of areticle stage for exposure including a switching (linking themeasurement values) operation of an encoder on the reticle side;

FIG. 11 is a view (No. 3) for describing a scanning operation of areticle stage for exposure including a switching (linking themeasurement values) operation of an encoder on the reticle side;

FIG. 12A is a view that shows a state in which the wafer stage islocated at a position where the area around the center of the wafer isdirectly under a projection unit;

FIG. 12B is a view that shows a state in which the wafer stage islocated at a position where the area in the middle between the center ofthe wafer and the periphery of the wafer is directly under theprojection unit;

FIG. 13A is a view that shows a state where the wafer stage is locatedat a position where the vicinity of the edge of the wafer on the +Y sideis directly under projection unit PU;

FIG. 13B is a view that shows a state where the wafer stage is locatedat a position where the vicinity of the edge of the wafer in a directionat an angle of 45 degrees to the X-axis and the Y-axis when viewing fromthe center of the wafer is directly under projection unit PU;

FIG. 14 is a view that shows a state where the wafer stage is located ata position where the vicinity of the edge of the wafer on the +X side isdirectly under projection unit PU;

FIG. 15 is a diagram that shows an example of a map which is obtained bya first calibration operation of encoders 26A₁, 26B₁, and 26C₁;

FIG. 16 is a view (No. 1) used for describing a second calibrationoperation for calibrating measurement errors of encoders 26A₁, 26B₁, and26C₁;

FIG. 17 is a view (No. 2) used for describing a second calibrationoperation for calibrating measurement errors of encoders 26A₁, 26B₁, and26C₁;

FIG. 18 is a view that shows an example of a map which is obtained by asecond calibration operation;

FIG. 19 is a diagram that shows an example of a map which is obtained bya second calibration operation of encoders 26A₁, 26B₁, and 26C₁;

FIG. 20 is a view used for describing a long-term calibration operation(a first calibration operation) of encoder values 50A to 50D, that is, aview used for describing an acquisition operation of correctioninformation of a grating pitch of a movement scale and correctioninformation of grating deformation;

FIG. 21 is a view that shows measurement values of an interferometer andan encoder which can be obtained through sequential calibration ofmeasurement errors of the encoder;

FIG. 22 is a view (No. 1) used for describing an acquisition operationof correction information of a grating pitch of movement scales 44A and44C related to a modified example;

FIG. 23 is a view (No. 2) used for describing an acquisition operationof correction information of a grating pitch of movement scales 44A and44C related to a modified example;

FIG. 24 is a view used for describing an acquisition operation ofcorrection information of a grating line deformation (grating line warp)of movement scales 44B and 44D related to a modified example;

FIG. 25 is a view that shows a modified example of an encoder system fora wafer stage;

FIG. 26 is a view that shows a different modified example of an encodersystem for a wafer stage; and

FIG. 27 is a view that shows a modified example of a wafer stage used ina liquid immersion exposure apparatus.

DESCRIPTION OF THE EMBODIMENTS

An embodiment of the present invention will be described below,referring to FIGS. 1 to 21.

FIG. 1 shows the entire configuration of an exposure apparatus 100related to the embodiment. Exposure apparatus 100 is a scanning exposureapparatus based on a step-and-scan method, that is, the so-calledscanning stepper. As it will be described later, a projection opticalsystem PL is arranged in the embodiment, and in the description below, adirection parallel to an optical axis AX of projection optical system PLwill be set as the Z-axis direction, a direction in which a reticle anda wafer are relatively scanned within a plane orthogonal to the Z-axiswill be set as the Y-axis direction, and a direction orthogonal to boththe Z-axis and Y-axis will be set as the X-axis direction. Further, therotational (gradient) direction around the X-axis, Y-axis, and Z-axiswill be set as θx direction, θy direction, and θz direction,respectively.

Exposure apparatus 100 is equipped with an illumination system 10 thatincludes a light source and an illumination optical system andilluminates reticles R1 and R2 with an illumination light (exposurelight) IL, a reticle stage RST that holds reticles R1 and R2, aprojection unit PU, a wafer stage unit 12 that includes a wafer stageWST on which a wafer W is mounted, a body BD on which reticle stage RST,projection unit PU and the like are mounted, a control system for thesecomponents and the like.

Illumination system 10 illuminates a slit shaped illumination area IAR(refer to FIG. 2) that extends in the X-axis direction set with areticle blind (masking system) (not shown) on reticle R1 or R2 by anillumination light IL with a substantially uniform illuminance. In thiscase, as illumination light IL, an ArF excimer laser beam (wavelength193 nm) is used.

Reticle stage RST is supported on a reticle base 36 that configures thetop plate of a second column 34 of reticle base 36, for example, via aclearance of several μm by air bearings or the like (not shown) arrangedon its bottom surface. As reticle stage RST, for example, a reticlestage that can hold one reticle, or a twin reticle stage that can moveindependently while each holding one reticle can be used. In thisembodiment, a reticle stage by a double reticle holder method that canhold two reticles at a time is used.

Reticle stage RST, in this case, can be finely driven two-dimensionally(in the X-axis direction, the Y-axis direction, and the θz direction)within an XY plane perpendicular to optical axis AX of projectionoptical system PL by a reticle stage drive system 11 which includes alinear motor or the like. Further, reticle stage RST can be driven onreticle base 36 in a predetermined scanning direction (in this case, theY-axis direction, which is the lateral direction of the page surface inFIG. 1) at a designated scanning speed. Reticle stage RST can employ acoarse/fine movement structure as is disclosed in, for example, Kokai(Japanese Patent Unexamined Application Publication) No. 8-130179 (thecorresponding U.S. Pat. No. 6,721,034), and its configuration is notlimited to the one referred to in this embodiment (FIG. 2 or the like).

Reticle stage RST is configured so that its positional informationwithin the XY plane (movement plane) can be measured by a reticleinterferometer system, which includes a reticle Y laser interferometer(hereinafter referred to as “reticle Y interferometer”) 16 y and thelike, and an encoder system, which includes encoder head (hereinaftersimply referred to as “head”) 26A₁ to 26A₃, 26C₁ to 26C₃, a movementscale 24A and the like. FIG. 1 shows a state where the upper edgesurface of reticles R1 and R2 are exposed above movement scale 24A.However, this is for the sake of convenience when describing theembodiment, therefore, the actual state will be different.

The configuration and the like of reticle stage RST, and the reticleinterferometer system and encoder system that measure the position ofreticle stage RST within the XY plane (movement plane) will be furtherdescribed below.

As is shown in FIG. 2, in the center of reticle stage RST, a rectangularrecessed section 22 is formed, which extends narrowly in the Y-axisdirection (the scanning direction) in a planar view (when viewed fromabove). Inside recessed section 22, two substantially square openings(not shown) are formed side by side in the Y-axis direction, and in astate covering these openings reticle R1 and reticle R2 are placed sideby side in the Y-axis direction. Reticles R1 and R2 are each vacuumsuctioned by a suction mechanism (not shown) such as, for example, avacuum chuck, which is arranged on the bottom surface within recessedsection 22 in the two openings, on both sides in the X-axis direction.

Further, on the +X side edge section and −X side edge section on theupper surface of reticle stage RST, a pair of movement scales 24A and24B are arranged with the Y-axis direction being the longitudinaldirection, in an arrangement symmetric to a center axis parallel to theY-axis direction that passes the center of illumination area IAR (in theembodiment, the center substantially coincides with optical axis AXwithin a first plane (object plane) of projection optical system PL).Movement scales 24A and 24B are made of the same material (such as, forexample, ceramics or low thermal expansion glass), and on the surface, areflection type diffraction grating that has a period direction in theY-axis direction is formed in an arrangement symmetric to the centeraxis referred to above. Movement scales 24A and 24B are fixed to reticlestage RST, for example, by vacuum suction (or a plate spring) or thelike, so that expansion/contraction does not occur locally.

Above movement scales 24A and 24B (on the +Z side), as is shown in FIG.2, two pairs of heads 26A₁ and 26A₂, and 26B₁ and 26B₂ used formeasuring the position in the Y-axis direction are arranged facingmovement scales 24A and 24B, in an arrangement symmetric to the centeraxis referred to above (refer to FIG. 1). Of these heads, heads 26A₁ and26B₁ are placed at positions where their measurement centerssubstantially coincide with a straight line (measurement axis) in theX-axis direction that passes the center of illumination area IARpreviously described. Further, heads 26A₂ and 26B₂ are placed atpositions the same distance away from heads 26A₁ and 26B₁ in the +Ydirection, also in plane with heads 26A₁ and 26B₁. Furthermore, also inplane with heads 26A₁ and 26B₁ and in symmetry with heads 26A₂ and 26B₂regarding the above measurement axis, a pair of heads 26A₃ and 26B₃ isplaced at positions the same distance away from heads 26A₁ and 26B₁ inthe −Y direction. The three pairs of heads 26A₁ and 26B₁, 26A₂ and 26B₂,and 26A₃ and 26B₃ are each fixed to reticle base 36 via support members(not shown).

Further, on the −X side of movement scale 24A on the upper surface ofreticle stage RST, a movement scale 28 with the Y-axis direction beingthe longitudinal direction is placed in line with movement scale 24A,and is fixed to reticle stage RST by, for example, vacuum suction (or aspring plate) or the like. Movement scale 28 is made of the samematerial as movement scales 24A and 24B (such as, for example, ceramicsor low thermal expansion glass), and on the upper surface, a reflectiontype diffraction grating that has a period direction in the X-axisdirection is formed covering almost the entire length in the Y-axisdirection.

Above movement scale 28 (on the +Z side), as is shown in FIG. 2, twoheads 26C₁ and 26C₂ used for measuring the position in the X-axisdirection are arranged facing movement scale 28 (refer to FIG. 1). Ofthese heads, head 26C₁ is positioned substantially on the straight line(measurement axis) in the X-axis direction that passes the center ofillumination area IAR previously described. Further, head 26C₂ is placedat a position in the vicinity of head 26A₂, which is a predetermineddistance away from head 26C₁ in the +Y direction, and also in plane withheads 26A₁ and 26A₂.

Furthermore, also in plane with head 26C₁ and in symmetry with head 26C₂regarding the above measurement axis, a head 26C₃ is placed at aposition a predetermined distance away from head 26C₁ in the −Ydirection. The three heads 26C₁, 26C₂, and 26C₃ are each fixed toreticle base 36 via support members (not shown). In the embodiment, thenine heads 26A₁ to 26A₃, 26B₁ to 26B₃, and 26C₁ to 26C₃ are fixed toreticle base 36 via support members (not shown), however, the presentinvention is not limited to this, and for example, the heads can bearranged in a frame member set on a floor surface F or a base plate BSvia a vibration isolation mechanism.

In the embodiment, heads 26A₁ and 26B₁ and movement scales 24A and 24Bthat face the heads constitute a pair of Y linear encoders used formeasuring the position of reticle stage RST in the Y-axis direction (Yposition). In the description below, for the sake of convenience, theseY linear encoders will be indicated as Y linear encoders 26A₁ and 26B₁using the same reference numerals as the heads.

The measurement axes of Y linear encoders 26A₁ and 26B₁ are located thesame distance away in the X-axis direction from the center ofillumination area IAR (in the embodiment, coinciding with optical axisAX of projection optical system PL) previously described. And, at thepoint of exposure or the like, for example, the Y position of reticlestage RST is measured, based on an average value of the measurementvalues of Y linear encoders 26A₁ and 26B₁. More specifically, thesubstantial measurement axes for measuring the positional information ofreticle stage RST with Y linear encoders 26A₁ and 26B₁ passes throughoptical axis AX of projection optical system PL. Accordingly, at thepoint of exposure or the like, the Y position of reticle stage RST canbe measured using Y linear encoders 26A₁ and 26B₁ without Abbe errors.Furthermore, rotational information of reticle stage RST in the θzdirection (yawing) is obtained based on the measurement values of Ylinear encoders 26A₁ and 26B₁.

Similarly, heads 26A₂ and 26A₃ and movement scale 24A that faces theheads each constitute a Y linear encoder used for measuring the positionof reticle stage RST in the Y-axis direction (Y position). In thedescription below, for the sake of convenience, these Y linear encoderswill each be indicated as Y linear encoders 26A₂, 26A₃, 26B₂, and 26B₃using the same reference numerals as the heads.

Further, head 26C₁ and movement scale 28 that face the head constitutean X linear encoder used for measuring the position of reticle stage RSTin the X-axis direction (an X position) along the straight line parallelto the X-axis direction (measurement axis) that passes through thecenter of illumination area IAR previously described. In the descriptionbelow, for the sake of convenience, the X linear encoder will beindicated as X linear encoder 26C₁ using the same reference numerals asthe head. Accordingly, at the point of exposure or the like, the Xposition of reticle stage RST can be measured using X linear encoder26C₁ without Abbe errors.

Similarly, heads 26C₂ and 26C₃ and movement scale 28 each constitute anX linear encoder used for measuring the X position of reticle stage RST.In the description below, for the sake of convenience, these X linearencoders will each be indicated as X linear encoders 26C₂ and 26C₃ usingthe same reference numerals as the heads.

The measurement values of the nine linear encoders (hereinafter willalso be appropriately referred to as “encoders”) 26A₁ to 26C₃ above aresent (refer to FIG. 3) to a main controller 20 (refer to FIG. 1).

The three movement scales 24A, 24B, and 28 are set so that their lengthin the Y-axis direction (corresponding to the formation range of thediffraction gratings in movement scales 24A and 24B, and the width ofthe diffraction grating in movement scale 28) covers the entire area ofthe movement strokes (movement range) of reticle stage RST in the Y-axisdirection when scanning exposure of wafer W is performed via at leastone of reticle R1 and R2 (in the embodiment, in at least during thescanning exposure and also during acceleration/deceleration andsynchronous settling period of reticle stage RST before and after thescanning exposure, among heads 26A_(i), 26B_(i), and 26C_(i) (i=1 to 3),which make a set in threes, at least one set of heads (measurementbeams) is set so that it does not move off its corresponding movementscale (diffraction grating), that is, an unmeasurable state is avoided).Further, the width (corresponding to the width of the diffractiongratings in movement scales 24A and 24B, and the formation range of thediffraction grating in movement scale 28) of the three movement scales24A, 24B, and 28 in the X-axis direction previously described is alsosimilarly set, so that it covers the entire area of the movement strokesof reticle stage RST in the X-axis direction (in the embodiment, amongheads 26A_(i), 26B_(i), and 26C_(i) (i=1 to 3), which make a set inthrees, at least one set of heads (measurement beams) is set so that itdoes not move off its corresponding movement scale (diffractiongrating), that is, an unmeasurable state is avoided). Reticle stage RSTcan be finely rotated in the θz direction, therefore, the size (lengthand width) of the three movement scales 24A, 24B, and 28 describedearlier in the X-axis and Y-axis directions is naturally decided alsotaking into consideration the rotational range in the θz direction, sothat measurement by at least the three linear encoders 26A₁, 26B₁, and26C₁ does not become unmeasurable.

Furthermore, in the embodiment, in the scanning exposure using reticleR2, the positional information (including at least the positions in theX-axis and Y-axis directions and the rotational direction in the θzdirection) of reticle stage RST can be measured by the six linearencoders 26A₁, 26A₂, 26B₁, 26B₂, 26C₁, and 26C₂. Further, in thescanning exposure using reticle R1, the positional information(including at least the positions in the X-axis and Y-axis directionsand the rotational direction in the θz direction) of reticle stage RSTcan be measured by the six linear encoders 26A₁, 26A₃, 26B₁, 26B₃, 26C₁,and 26C₃. Further, in the embodiment, exchange of reticles R1 and R2 isperformed on the +Y side or the −Y side with respect to illuminationarea IAR previously described, or reticle R1 is exchanged on the −Y sidewhile reticle R2 is exchanged on the +Y side, and also at such exchangepositions, the positional information of reticle stage RST can bemeasured using at least three of the linear encoders 26A₂, 26B₂, and26C₂ or linear encoders 26A₃, 26B₃, and 26C₃.

In the embodiment, the encoder system for reticle stage RST isconfigured with the three movement scales 24A, 24B, and 28 and a headunit that has nine heads 26A₁ to 26A₃, 26B₁ to 26B₃, and 26C₁ to 26C₃,however, the configuration of the encoder system is not limited to theone shown in FIG. 2, and for example, the head unit can merely havethree head units, 26A₁, 26B₁, and 26C₁. In this case, when the positionof reticle stage RST becomes unmeasurable by linear encoders 26A₁, 26B₁,and 26C₁ at the reticle exchange position or while moving to the reticleexchange position, the position of reticle stage RST can be measured,for example, using a different measurement unit, or at least a part ofthe reticle interferometer system referred to earlier. Further, in theembodiment, the three movement scales 24A, 24B, and 28 are fixed toreticle stage RST using a suction mechanism, a plate spring or the like,however, besides such ways, for example, a screw clamp can be used, orthe diffraction grating can be directly formed on reticle stage RST.Furthermore, in the embodiment, movement scales 24A, 24B, and 28 arearranged on the upper surface (illumination system side) of reticlestage RST, however, movement scales 24A, 24B, and 28 can also bearranged on the lower surface (projection optical system side), or theplacement of the head units (encoder heads) and movement scales 24A,24B, and 28 described earlier can be reversed, that is, the head unitscan be arranged on reticle stage RST and movement scales 24A, 24B, and28 can be arranged on the body side.

The reticle interferometer system is equipped with reticle Yinterferometer 16 y and a reticle X interferometer 16 x, as is shown inFIGS. 2 and 6.

As is shown in FIG. 2, reticle X interferometer 16 x includes a sensorhead 19A (not shown in FIG. 1) and an optical system unit 19B fixed tothe edge surface of reticle stage RST on the +X side.

Sensor head 19A is fixed on the upper surface of reticle base 36, andsensor head 19A incorporates a light source, an optical system, twoanalyzers (polarizers), and two photoelectric conversion elementsinside. As the light source, a two-frequency laser that uses the Zeemaneffect is used. The optical system enlarges the sectional shape of thelaser beam from this light source in the horizontal direction, and as isshown in FIG. 2, a beam BM whose sectional shape is enlarged is emittedfrom sensor head 19. Then, in optical system unit 19B, beam BM is splitinto two beams, and one of the split beams is incident on a first beamsplitter (not shown), which splits the beam into a measurement beam BM₁and a reference beam. Measurement beam BM₁ is reflected by a reflectionsurface of a planar mirror 21, while the reference beam is reflected,for example, by the reflection surface of reticle stage RST, and thenreturns to the first beam splitter where it is concentricallysynthesized and then is output from optical system unit 19B. Similarly,the other split beam is incident on a second beam splitter (not shown),which splits the beam into a measurement beam BM₂ and a reference beam.Measurement beam BM₂ is reflected by a reflection surface of a planarmirror 21, while the reference beam is reflected, for example, by thereflection surface of reticle stage RST, and then returns to the secondbeam splitter where it is concentrically synthesized and then is outputfrom optical system unit 19B. Although it is not shown in the drawings,in the embodiment, planar mirror 21 is fixed to a part of body BDdescribed earlier, such as, for example, to reticle base 36 of thesecond column 34, or to a barrel platform (main frame) 38 of a firstcolumn 32 which will be described later in the description.

Further, return lights from both the first and the second beam splittersinside optical system unit 19B (synthesized light of measurement beamsBM₁ and BM₂ and the respective reference beams described above) returnto sensor head 19A. Inside sensor head 19A, these return lights areincident on separate analyzers via the optical system, and theinterference lights output from each analyzer are received separately bythe two photoelectric conversion elements, and interference signalsaccording to each of the interference lights are sent to a signalprocessing system (not shown). Then, based on the interference signalsof each photoelectric conversion element, the signal processing systemuses a phase change that occurs due to a Doppler shift in the phase ofthe measurement beam with respect to the phase of the reference beam toperform a heterodyne detection for measuring the change in theinterference signals caused by the phase change. And then, from thechange of the interference signals that have been detected, the signalprocessing system constantly detects the positional information ofreticle stage RST in the X-axis direction at the irradiation points ofmeasurement beams BM₁ and BM₂ with planar mirror 21 serving as areference, that is, the X positional information of reticle stage RST atthe irradiation points of measurement beams BM₁ and BM₂, at a resolutionof, for example, approximately 0.5 to 1 nm.

Reticle Y interferometer 16 y is a Michelson heterodyne interferometerthat employs a two-frequency laser that uses the Zeeman effect as itslight source as in reticle X interferometer 16 x. Reticle Yinterferometer 16 y constantly detects the Y position of reticle stageRST via a movable mirror (such as a planar mirror or a retroreflector)15, which is fixed to reticle stage RST, at a resolution of, forexample, approximately 0.5 to 1 nm, with a fixed mirror 14 (refer toFIG. 1) fixed to the side surface of a barrel 40 configuring projectionunit PU serving as a reference. At least a part of reticle Yinterferometer 16 y (for example, an optical unit excluding the lightsource) is fixed, for example, to reticle base 36.

The X positional information from the two axes of reticle Xinterferometer 16 x and the Y positional information from reticle Yinterferometer 16 y is sent to main controller 20 (refer to FIG. 6).

The reticle interferometer system previously described is equipped withX interferometer 16 x that has sensor head 19A and optical system unit19B arranged in reticle stage RST, however, the configuration of Xinterferometer 16 x is not limited to this, and for example, thearrangement of optical system unit 19B and planar mirror 21 can bereversed, or more specifically, a configuration in which a measurementbeam from optical system unit 19B placed on reticle base 36 isirradiated on a reflection surface (corresponding to planar mirror 21)formed extending in the Y-axis direction on the side surface of reticlestage RST can also be employed. Furthermore, sensor head 19A is arrangedon reticle base 36, however, for example, at least a part of sensor head19A can be arranged on a frame member different from body BD. Further,in the embodiment, as the reflection surface for the interferometer ofthe reticle interferometer system, movable mirror 15 referred to earlierfixed on the edge surface of reticle stage RST is used, however, insteadof movable mirror 15, a reflection surface, which can be obtained bymirror polishing the edge surface (side surface) of reticle stage RST,can also be used. Further, in the embodiment, Y interferometer 16 y hadone measurement axis and X interferometer 16 x had two measurement axes,however, the number of measurement axis can be reversed between theX-axis direction and the Y-axis direction, or both of theinterferometers can each have two or more axes. Especially in the lattercase, Y interferometer 16 y can measure the rotational information inthe θx direction (pitching) of reticle stage RST and X interferometer 16x can measure the rotational information in the θy direction (rolling)of reticle stage RST.

In exposure apparatus 100 of the embodiment, the measurement values ofreticle interferometer systems 16 x and 16 y are used only forcalibration of measurement values of encoders 26A₁, 26B₁, 26C₁ and thelike, which will be described later, and on exposure operation, theposition of reticle stage RST is controlled according to measurementvalues of the encoder system on the reticle side. Especially theposition of reticle stage RST during scanning exposure is controlled bymain controller 20, based on the measurement values of encoders 26A₁,26B₁, and 26C₁. Accordingly, as it can be easily imagined from FIG. 2,on exposure operation, a switching operation (linking the measurementvalues) of the encoder used for position control of reticle stage RSThas to be performed. Details will be described later in the description.

Above reticle stage RST, a pair of reticle alignment detection systems13A and 13B (not shown in FIG. 1, refer to FIG. 6), each consisting ofan alignment system by a TTR (Through The Reticle) method that useslight of the exposure wavelength for detecting a pair of fiducial markson wafer stage WST and a corresponding pair of reticle marks on thereticle at the same time via projection optical system PL, is arrangedin the X-axis direction at a predetermined distance. As the pair ofreticle alignment detection systems 13A and 13B, a system having astructure similar to the one disclosed in, for example, Kokai (JapaneseUnexamined Patent Application Publication) No. 7-176468 (thecorresponding U.S. Pat. No. 5,646,413) and the like can be used.

Projection unit PU is held by a part of body BD, below reticle stage RSTin FIG. 1. Body BD is equipped with the first column 32 arranged onframe caster FC installed on floor surface F of a clean room and thesecond column 34 fixed on the first column 32.

Frame caster FC is equipped with a base plate BS laid horizontally onfloor surface F, and a plurality of, e.g. three (or four), leg sections39 (however, the leg section in the depth of the page surface of FIG. 1is omitted in the drawings) fixed on base plate BS.

The first column 32 is equipped with a barrel platform (main frame) 38,which is supported substantially horizontally by a plurality of, e.g.three (or four), first vibration isolation mechanisms 58 fixedindividually on the upper end of the plurality of leg sections 39 thatconfigures frame caster FC.

In barrel platform 38, a circular opening (not shown) is formedsubstantially in the center, and in the circular opening, projectionunit PU is inserted from above and is held by barrel platform 38 via aflange FLG arranged on the outer circumferential section. On the uppersurface of barrel platform 38, at positions surrounding projection unitPU, one end (the lower end) of a plurality of, e.g. three (or four),legs 41 (however, the leg in the depth of the page surface of FIG. 1 isomitted in the drawings) is fixed. The other end (the upper end) ofthese legs 41 is substantially flush on a horizontal surface, and oneach of the upper end surface of legs 41, the lower surface of reticlebase 36 described earlier is fixed. In the manner described above, theplurality of legs 41 horizontally supports reticle base 36. That is,reticle base 36 and legs 41 that support reticle base 36 constitute thesecond column 34. In reticle base 36, an opening 36 a, which serves as apath for illumination light IL, is formed in the center.

Projection unit PU includes barrel 40 that has a cylinder hollow shapewith flange FLG arranged, and projection optical system PL consisting ofa plurality of optical elements held in barrel 40. In the embodiment,projection unit PU was mounted on barrel platform 38, however, as isdisclosed in, for example, the pamphlet of International PublicationWO2006/038952 and the like, projection unit PU can be supported bysuspension with respect to a mainframe member (not shown) placed aboveprojection unit PU or to reticle base 36.

As projection optical system PL, for example, a dioptric system is usedconsisting of a plurality of lenses (lens elements) that are disposedalong optical axis AX, which is parallel to the Z-axis direction.Projection optical system PL is, for example, a both-side telecentricdioptric system that has a predetermined projection magnification (suchas one-quarter or one-fifth times). Therefore, when illumination lightIL from illumination system 10 illuminates illumination area IAR, areduced image of the circuit pattern (a reduced image of a part of thecircuit pattern) is formed within illumination area IAR, withillumination light IL that has passed through the reticle (R1 or R2)whose pattern surface substantially coincides with the first plane(object plane) of projection optical system PL, in an area conjugate toillumination area IAR on wafer W (exposure area) whose surface is coatedwith a resist (a sensitive agent) and is placed on the second plane(image plane) side, via projection optical system PL. And by reticlestage RST and wafer stage WST being synchronously driven, the reticle isrelatively moved in the scanning direction (Y-axis direction) withrespect to illumination area IAR (illumination light IL) while wafer Wis relatively moved in the scanning direction (Y-axis direction) withrespect to the exposure area (illumination light IL), thus scanningexposure of a shot area (divided area) on wafer W is performed, and thepattern of the reticle is transferred onto the shot area. That is, inthe embodiment, the pattern is generated on wafer W according toillumination system 10, the reticle, and projection optical system PL,and then by the exposure of the sensitive layer (resist layer) on waferW with illumination light IL, the pattern is formed on wafer W.

Wafer stage unit 12 is equipped with a stage base 71, which is supportedsubstantially horizontally by a plurality of (e.g. three) secondvibration isolation mechanisms (omitted in drawings) placed on baseplate BS, wafer stage WST placed above the upper surface of stage base71, a wafer stage drive section 27 that drives wafer stage WST, and thelike.

Stage base 71 is made of a flat plate, which is also called a platform,and the upper surface is finished so that the degree of flatness isextremely high. The upper surface serves as a guide surface when waferstage WST moves.

Wafer stage WST has a main section and a table section above the mainsection, and is driven, for example, in directions of six degrees offreedom, which are the X-axis direction, the Y-axis direction, theZ-axis direction, the θx direction, the θy direction, and the θzdirection by wafer stage drive system 27 that includes voice coil motorsor the like.

Wafer stage WST can also employ a configuration, for example, in whichwafer stage WST is equipped with a wafer stage main section driven in atleast the X-axis direction, the Y-axis direction, and the θz directionby a linear motor or the like, and a wafer table that is finely drivenon the wafer stage main section in at least the Z-axis direction, the θxdirection, and the θy direction by a voice coil motor or the like.

On wafer stage WST (or to be more precise, on the table sectionmentioned above), wafer W is mounted via a wafer holder (not shown), andwafer W is fixed to the wafer holder, for example, by vacuum suction (orelectrostatic suction) or the like.

Further, positional information of wafer stage WST within the XY plane(movement plane) can be measured by both an encoder system that includeshead units 46B, 46C, and 46D and movement scales 44B, 44C, and 44D andthe like and a wafer laser interferometer system (hereinafter referredto as “wafer interferometer system”) 18, shown in FIG. 1. Next, detailson the configuration of the encoder system for wafer stage WST and waferinterferometer system 18 will be described.

As is shown in FIG. 3, on the upper surface of wafer stage WST, fourmovement scales 44A to 44D are fixed surrounding wafer W. Morespecifically, movement scales 44A to 44D are made of the same material(such as, for example, ceramics or low thermal expansion glass), and onthe surface, a reflection type diffraction grating that has a perioddirection in the longitudinal direction is formed. The diffractiongrating is formed having a pitch, for example, between 4 μm to 138 nm.In this embodiment, the diffraction grating is formed having a 1 μmpitch. In FIG. 3, for the sake of convenience in the drawing, the pitchof the grating will be indicated much wider than the actual pitch. Thesame applies to other drawings.

The longitudinal direction of movement scales 44A and 44C coincides withthe Y-axis direction in FIG. 3, and movement scales 44A and 44C arearranged in symmetry with respect to a center line that passes throughthe center of wafer stage WST (considered excluding movable mirrors 17Xand 17Y) parallel to the Y-axis direction, and each diffraction gratingformed on movement scales 44A and 44C is also placed in symmetryregarding the center line. Since these movement scales 44A and 44C havediffraction gratings arranged periodically in the Y-axis direction,movement scales 44A and 44C are used for measuring the position of waferstage WST in the Y-axis direction.

Further, the longitudinal direction of movement scales 44B and 44Dcoincides with the X-axis direction in FIG. 3, and movement scales 44Band 44D are arranged in symmetry with respect to a center line thatpasses through the center of wafer stage WST (considered excludingmovable mirrors 17X and 17Y) parallel to the X-axis direction, and eachdiffraction grating formed on movement scales 44B and 44D is also placedin symmetry regarding the center line. Since these movement scales 44Band 44D have diffraction gratings arranged periodically in the X-axisdirection, movement scales 44B and 44D are used for measuring theposition of wafer stage WST in the X-axis direction.

In FIG. 1 the state is shown where wafer W is exposed above movementscale 44C, however, this is for the sake of convenience, and the uppersurface of movement scales 44A to 44D is actually at the same height, orpositioned above the upper surface of wafer W.

Meanwhile, as is obvious from FIGS. 1 and 3, four encoder head units(hereinafter shortened to “head unit”) 46A to 46D are placed crossingthe corresponding movement scales 44A to 44D, in a state where the fourencoder heads surround the periphery of the lowest end of projectionunit PU from four directions. Although it is omitted in FIG. 1 from thepoint of avoiding confusion, these head units 46A to 46D are actuallyfixed to barrel platform 38 in a suspended state via a support member.

Head units 46A and 46C are placed on the −X side and +X side ofprojection unit PU with the longitudinal direction being the X-axisdirection, which is orthogonal to the longitudinal direction of thecorresponding movement scales 44A and 44C (the Y-axis direction in FIG.3), and is also placed in symmetry regarding optical axis AX ofprojection optical system PL. Further, head units 46B and 46C are placedon the +Y side and −Y side of projection unit PU with the longitudinaldirection being the Y-axis direction, which is orthogonal to thelongitudinal direction of the corresponding movement scales 44B and 44D(the X-axis direction in FIG. 3), and is also placed in symmetryregarding optical axis AX of projection optical system PL.

Head units 46A to 46D can each be a unit that has, for example, a singlehead or a plurality of heads that are disposed seamlessly. In theembodiment, however, as in FIG. 3 representatively showing head unit46C, the head unit has a plurality of, e.g. eleven heads 48 a to 48 k,disposed at a predetermined distance in the longitudinal direction.Incidentally, in head units 46A to 46D, the plurality of heads aredisposed at a distance so that adjacent two heads of the plurality ofheads do not go astray from the corresponding movement scale(diffraction grating), or in other words, at around the same distance ornarrower than the width of the diffraction grating in the directionorthogonal to the longitudinal direction (disposal direction of thediffraction grating) of the movement scale.

Head unit 46A constitutes a multiple-lens type, or to be more accurate,an eleven-lens Y linear encoder 50A (refer to FIG. 6), which is equippedwith heads 48 a to 48 k, for measuring the Y position of wafer stage WSTalong with movement scale 44A. Further, head unit 46B constitutes aneleven-lens X linear encoder 50B (refer to FIG. 6) for measuring the Xposition of wafer stage WST along with movement scale 44B. Further, headunit 46C constitutes an eleven-lens Y linear encoder 50C (refer to FIG.6) for measuring the Y position of wafer stage WST along with movementscale 44C. Further, head unit 46D constitutes an eleven-lens X linearencoder 50D (refer to FIG. 6) for measuring the X position of waferstage WST along with movement scale 44D. The measurement values ofencoders 50A to 50D are sent to main controller 20. In the embodiment,the four head unit 46A to 46D are supported by suspension from barrelplatform 38, however, in the case exposure apparatus 100 of FIG. 1 has aconfiguration in which projection unit PU is supported by suspensionwith respect to a mainframe member or a reticle base 36, for example,head units 46A to 46D can be supported by suspension integrally withprojection unit PU, or the four head units 46A to 46D can be arrangedindependently from projection unit PU in a measurement frame supportedby suspension from the mainframe member or from reticle base 36.

Further, as is shown in FIG. 1, positional information of wafer stageWST is constantly detected by wafer interferometer system 18, whichirradiates measurement beams on movable mirrors 17 and 43 fixed on waferstage WST, at a resolution of, for example, approximately 0.5 to 1 nm.Wafer interferometer system 18 has at least a part of its system (forexample, the optical unit excluding the light source) fixed to barrelplatform 38 in a suspended state. At least a part of waferinterferometer system 18 can be supported by suspension integrally withprojection unit PU, or can be arranged in the measurement frame as isdescribed above.

As is shown in FIG. 3, on wafer stage WST, Y movable mirror 17Y that hasa reflection surface orthogonal to the Y-axis direction, which is thescanning direction, and X movable mirror 17X that has a reflectionsurface orthogonal to the X-axis direction, which is the non-scanningdirection, are actually arranged. In FIG. 1, however, these mirrors arerepresentatively shown as movable mirror 17.

As is shown in FIG. 3, wafer interferometer system 18 includes fiveinterferometers, which are; a wafer Y interferometer 18Y, two wafer Xinterferometers 18X₁ and 18X₂, and two Z interferometers 18Z₁ and 18Z₂.As these five interferometers, 18Y, 18X₁, 18X₂, 18Z₁, and 18Z₂, aMichelson heterodyne interferometer is used that employs a two-frequencylaser that uses the Zeeman effect. Of these interferometers, as wafer Yinterferometer 18Y, a multi-axis interferometer is used that has aplurality of measurement axes including two measurement axes, which aresymmetric with respect to an axis (center axis) parallel to the Y-axispassing through optical axis AX of projection optical axis AX (thecenter of the exposure area previously described) and the detectioncenter of an alignment system ALG, as is shown in FIG. 3.

Wafer X interferometer 18X₁ irradiates a measurement beam on movablemirror 17X along a measurement axis that passes through optical axis AXof projection optical system PL parallel to the X-axis. Wafer Xinterferometer 18X₁ measures the positional information of thereflection surface of movable mirror 17X, which uses the reflectionsurface of X fixed mirror fixed to the side surface of barrel 40 ofprojection unit PU as a reference, as the X position of wafer stage WST.

Wafer X interferometer 18X₂ irradiates a measurement beam on movablemirror 17X along a measurement axis that passes through the detectioncenter of alignment system ALG parallel to the X-axis, and measures thepositional information of the reflection surface of movable mirror 17X,which uses the reflection surface of a fixed mirror fixed to the sidesurface of alignment system ALG as a reference, as the X position ofwafer stage WST.

Further, on the side surface of the main section of wafer stage WST onthe +Y side, movable mirror 43 whose longitudinal direction is in theX-axis direction is attached via a kinematic support mechanism, as isshown in FIGS. 1 and 4.

A pair of Z interferometers 18Z₁ and 18Z₂ that constitutes a part ofinterferometer system 18 and irradiates a measurement beam on movablemirror 43 is arranged, facing movable mirror 43 (refer to FIGS. 3 and4). More particularly, as is shown in FIGS. 3 and 4, the length ofmovable mirror 43 in the X-axis direction is longer than movable mirror17Y, and is made of a member that has a hexagonal sectional shape, whichlooks like a rectangle and an isosceles trapezoid combined together.Mirror polishing is applied on the surface of movable mirror 34 on the+Y side, and three reflection surfaces 43 b, 43 a, and 43 c shown inFIG. 4 are formed.

Reflection surface 43 a configures the edge surface on the +Y side ofmovable mirror 43, and is parallel to the XZ plane as well as extendingin the X-axis direction. Reflection surface 43 b configures the surfaceadjacent to the +Z side of reflection surface 43 a, and is parallel to aplane tilted by a predetermined angle in a clockwise direction in FIG. 4with respect to the XZ plane and also extends in the X-axis direction.Reflection surface 43 c configures the surface adjacent to the −Z sideof reflection surface 43 a, and is arranged in symmetry with reflectionsurface 43 b with reflection 43 a in between.

As is obvious from FIGS. 3 and 4, Z interferometers 18Z₁ and 18Z₂ arerespectively arranged on one side and the other side of Y interferometer18Y in the X-axis direction, spaced apart at substantially the samedistance and also at a position slightly lower that Y interferometer18Y.

As is shown in FIGS. 3 and 4, Z interferometers 18Z₁ and 18Z₂ projectmeasurement beams B1 and B2 on reflection surfaces 43 b and 43 c,respectively, along the Y-axis direction. In the embodiment, a fixedmirror 47A that has a reflection surface on which measurement beam B1reflected off reflection surface 43 b is perpendicularly incident and afixed mirror 47B that has a reflection surface on which measurement beamB2 reflected off reflection surface 43 c is perpendicularly incident arearranged, each extending in the X-axis direction.

Fixed mirrors 47A and 47B are supported, for example, using the samesupport section (not shown) arranged in barrel platform 38.Incidentally, fixed mirrors 47A and 47B can also be supported using themeasurement frame previously described.

As is shown in FIG. 3, Y interferometer 18Y project measurement beams B4₁ and B4 ₂ on movable mirror 17Y, along the measurement axes in theY-axis direction, which are spaced apart by the same distance on the −Xside and +X side from a straight line parallel to the Y-axis passingthrough the projection center (optical axis AX, refer to FIG. 1) ofprojection optical system PL, and by receiving the respective reflectionbeams, Y interferometer 18Y detects the positional information of waferstage WST in the Y-axis direction at the irradiation point ofmeasurement beams B4 ₁ and B4 ₂ while using the reflection surface of aY fixed mirror fixed to the side surface of barrel 40 of projection unitPU as a reference. In FIG. 4, measurement beams B4 ₁ and B4 ₂ arerepresentatively shown as measurement beam B4.

Further, Y interferometer 18Y projects a measurement beam B3 towardreflection surface 43 a along a measurement axis, which is positionedsubstantially in the center between measurement beams B4 ₁ and B4 ₂ in aplanar view and also positioned at the −Z side of measurement beams B4 ₁and B4 ₂ in a side view, and by receiving measurement beam B3 reflectedoff reflection surface 43 a, Y interferometer 18Y detects the positionalinformation of reflection surface 43 a of movable mirror 43 (that is,wafer stage WST) in the Y-axis direction.

Main controller 20 computes the Y position of movable mirror 17Y, thatis wafer table WTB (wafer stage WST), based on an average value of themeasurement values of the measurement axes corresponding to measurementbeams B4 ₁ and B4 ₂ of Y interferometer 18Y. Further, main controller 20computes the displacement of wafer stage WST in the θx direction(pitching), based on the Y position of movable mirror 17Y and reflectionsurface 43 a of movable mirror 43.

Further, measurement beams B1 and B2 projected from Z interferometers18Z₁ and 18Z₂ are respectively incident on reflection surfaces 43 b and43 c of movable mirror 43 at a predetermined incident angle (the angleis θ/2), and are reflected off reflection surfaces 43 b and 43 c and areperpendicularly incident on the reflection surface of fixed mirrors 47Aand 47B. Then, measurement beams B1 and B2 reflected off fixed mirrors47A and 47B are respectively reflected again by reflection surfaces 43 band 43 c, and then are received by Z interferometers 18Z₁ and 18Z₂.

In the case the displacement of wafer stage WST (that is, movable mirror43) in the Y-axis direction is ΔYo and the displacement (movementamount) in the Z-axis direction is ΔZo, the optical path lengthvariation ΔL1 of measurement beam B1 and the optical path lengthvariation ΔL2 of measurement beam B1 received by Z interferometers 18Z₁and 18Z₂ can respectively expressed as in equations (1) and (2) below.

ΔL1≈ΔYo×cos θ−ΔZo×sin θ  (1)

ΔL2≈ΔYo×cos θ−ΔZo×sin θ  (2)

Accordingly, from equations (1) and (2), ΔZo and ΔYo can be obtained bythe following equations, (3) and (4).

ΔZo=(ΔL2−ΔL1)/2 sin θ  (3)

ΔYo=(ΔL2+ΔL1)/2 sin θ  (4)

The above displacements ΔZo and ΔYo are obtained by each of the Zinterferometers 18Z₁ and 18Z₂. Therefore, the displacements obtained byZ interferometer 18Z₁ will be ΔZoR and ΔYoR, and the displacementsobtained by Z interferometer 18Z₂ will be ΔZoL and ΔYoL, and in the casethe distance (spacing) of measurement beams B1 and B2 in the X-axisdirection is indicated as D (refer to FIG. 3), then the displacement ofmovable mirror 43 (that is, wafer stage WST) in the θz direction (yawingamount) Δθz and the displacement of movable mirror 43 (that is, waferstage WST) in the θy direction (rolling amount) Δθy can be obtained fromequations (5) and (6) below.

Δθz=(ΔYoR−ΔYoL)/D  (5)

Δθy=(ΔZoL−ΔZoR)/D  (6)

Accordingly, by using the above equations (1) to (6), main controller 20can compute the displacement of wafer stage WST in four degrees offreedom, ΔZo, ΔYo, Δθz, and Δθy, based on the measurement results of Zinterferometers 43A and 43B.

Further, as is described above, main controller 20 can obtaindisplacement ΔY of wafer stage WST in the Y-axis direction anddisplacement (pitching amount) Δθx of wafer stage WST in the θxdirection, based on the measurement results of Y interferometer 18Y.

Incidentally, in FIG. 1, X interferometers 18X₁ and 18X₂ and Zinterferometers 18Z₁ and 18Z₂ are representatively shown as waferinterferometer system 18, and the fixed mirrors for measuring theposition in the X-axis direction and the fixed mirrors for measuring theposition in the Y-axis direction are representatively shown as fixedmirror 57. Further, alignment system ALG and the fixed mirror fixed toalignment system ALG are omitted in FIG. 1.

In the embodiment, wafer X interferometer 18X₁ and wafer Yinterferometer 18Y are used for calibration of the encoder system usedwhen performing scanning exposure of the wafer, whereas wafer Xinterferometer 18X₂ and wafer Y interferometer 18Y are used for markdetection performed by alignment system ALG. Further, besides measuringthe Y position of wafer stage WST, wafer Y interferometer 18Y can alsomeasure the rotational information in the θx direction (pitching). Inthe embodiment, as the reflection surfaces of the measurement beams of Xinterferometers 18X₁ and 18X₂ and Y interferometer 18Y of waferinterferometer system 18 previously described, movable mirrors 17X and17Y fixed to wafer stage WST were used, however, the embodiment is notlimited to this, and for example, the edge surface (side surface) ofwafer stage WST can be mirror polished so as to form a reflectionsurface (corresponding to the reflection surface of movable mirrors 17Xand 17Y).

The measurement values of wafer Y interferometer 18Y, X interferometers18X₁ and 18X₂, and Z interferometers 18Z₁ and 18Z₂ are supplied to maincontroller 20.

Further, on wafer stage WST, a fiducial mark plate (not shown) is fixedin a state where the surface is at the same height as wafer W. On thesurface of this fiducial plate, at least a pair of a first fiducialmarks used for reticle alignment, a second fiducial mark used forbaseline measurement of alignment system ALG whose positional relationto the first fiducial mark is known and the like are formed.

In exposure apparatus 100 of the embodiment, although it is omitted inFIG. 1, a multiple point focal position detection system by an obliqueincident method consisting of an irradiation system 42 a and aphotodetection system 42 b (refer to FIG. 6) similar to the onedisclosed in, for example, Kokai (Japanese Patent Unexamined ApplicationPublication) No. 6-283403 (the corresponding U.S. Pat. No. 5,448,332) orthe like is arranged.

Further, in exposure apparatus 100, in the vicinity of projection unitPU, an alignment system ALG is arranged (not shown in FIG. 1). As thisalignment system ALG, for example, a sensor of an FIA (Field ImageAlignment) system by an image-processing method is used. This alignmentsystem ALG supplies positional information of marks using index centeras a reference to main controller 20. Based on the information that hasbeen supplied and the measurement values of interferometers 18Y and 18X₂of wafer interferometer system 18, main controller 20 measures thepositional information of the marks subject to detection, or to be morespecific, measures the positional information of the second fiducialmarks on the fiducial mark plate or the alignment marks on the wafer ona coordinate system (alignment coordinate system), which is set byinterferometers 18Y and 18X₂.

Next, the configuration or the like of encoders 50A to 50D will bedescribed, focusing representatively on encoder 50C shown enlarged inFIG. 5. In FIG. 5, heads 48 a to 48 k (FIG. 3) of head unit 46C, whichirradiates a detection beam on movement scale 44C, are indicated as asingle head, as a head 48 y.

Head 48 y can be roughly divided into three sections, which are; anirradiation system 64 a, an optical system 64 b, and a photodetectionsystem 64 c.

Irradiation system 64 a includes a light source that emits laser beam LBat an angle of 45 degrees with respect to the Y-axis and the Z-axis,such as, for example, a semiconductor laser LD, and a lens L1 placed onthe optical path of laser beam LB emitted from semiconductor laser LD.

Optical system 64 b is equipped with parts such as a polarization beamsplitter PBS whose separating plane is parallel to the XZ plane, a pairof reflection mirrors R1 a and R1 b, lenses L2 a and L2 b, quarter-waveplates (hereinafter referred to as λ/4 plates) WP1 a and WP1 b,reflection mirrors R2 a and R2 b, and the like.

Photodetection system 64 c includes polarizers (analyzers),photodetectors and the like.

In encoder 50C, laser beam LB emitted from semiconductor laser LD isincident on polarization beam splitter PBS via lens L1, and is split bypolarization into two beams, LB₁ and LB₂. Beam LB₁ that has transmittedpolarization beam splitter PBS reaches a reflection diffraction gratingRG formed on movement scale 44C via reflection mirror R1 a, whereas beamLB₂ that has been reflected off polarization beam splitter PBS reachesreflection diffraction grating RG via reflection mirror Rib. “Split bypolarization,” in this case, means that the incident beam is separatedinto a P polarization component and an S polarization component.

Diffraction beams of a predetermined order, for example, first orderdiffraction beams, are generated from diffraction grating RG by theirradiation of beams LB₁ and LB₂, and after the beams are respectivelyconverted to a circular polarized light by λ/4 plates WP1 a and WP1 bvia lenses L2 b and L2 a, the beams are then reflected by reflectionmirrors R2 a and R2 a and pass through λ/4 plates WP1 a and WP1 b again,and reach polarization beam splitter PBS while passing through the sameoptical path in a reversed direction.

The polarized directions of each of the two beams that have reachedpolarization beam splitter PBS are rotated at an angle of 90 degreeswith respect to the original direction. Therefore, the first orderdiffraction beam of beam LB₁ that has transmitted polarization beamsplitter PBS earlier is reflected by polarization beam splitter PBS andis incident on photodetection system 64 c, and the first orderdiffraction beam of beam LB₂ that has been reflected by polarizationbeam splitter PBS earlier transmits polarization beam splitter PBS andis synthesized concentrically with the first order diffraction beam ofbeam LB₁ and then is incident on photodetection system 64 c.

Then, inside photodetection system 64 c, the analyzers uniformly arrangethe polarized directions of the two first order diffraction beams aboveso that the beams interfere with each other and become an interferencelight. The interference beam is detected by the photodetectors, and isconverted into electric signals according to the intensity of theinterference light.

As is obvious from the description above, in encoder 50C, since theoptical path lengths of the two beams that are made to interfere areextremely short and are substantially equal, the influence of airfluctuation can mostly be ignored. Then, when movement scale 44 (thatis, wafer stage WST) moves in the measurement direction (in this case,the Y-axis direction), the phase of each of the two beams change and theintensity of the interference light changes. This change in intensity ofthe interference light is detected by photodetection system 64 c, andthe positional information according to the intensity change is outputas the measurement values of encoder 50C. The other encoders 50A, 50B,and 50D are also configured similar to encoder 50C. Further, also forthe nine encoders 26A₁ to 26C₃ for the reticle stage, an encoder by thediffraction interference method that has a configuration similar toencoder 50C is used. And, as each encoder, an encoder that has aresolution of, for example, approximately 0.1 nm is used.

FIG. 6 shows a block diagram, which is partially omitted, of a controlsystem related to stage control of exposure apparatus 100 of theembodiment. The control system in FIG. 6 is configured including aso-called microcomputer (or workstation) made up of a CPU (CentralProcessing Unit), ROM (Read Only Memory), RAM (Random Access Memory),and the like, and is mainly composed of main controller 20, which servesas a control unit that controls the overall operation of the entireapparatus.

In exposure apparatus 100 that has the configuration described above,when wafer alignment operation is performed by the EGA (Enhanced GlobalAlignment) method or the like disclosed in, for example, Kokai (JapaneseUnexamined Patent Application Publication) No. 61-44429 and thecorresponding U.S. Pat. No. 4,780,617 and the like, the position ofwafer stage WST is controlled by main controller 20 based on themeasurement values of wafer interferometer system 18 as is describedabove, and at the time besides wafer alignment operation such as, forexample, during exposure operation, the position of wafer stage WST iscontrolled by main controller 20 based on the measurement values ofencoders 50A to 50D. Incidentally, the position of wafer stage WST canbe controlled based on the measurement values of encoders 50A to 50Dalso when wafer alignment operation is performed. Further, in the casethe position of wafer stage WST is controlled based on the measurementvalues of encoders 50A to 50D when wafer alignment operation isperformed, at least one of the measurement values of waferinterferometer system 18 (e.g. positional information of the Z-axis, theθx, and the θy direction) can also be used together.

Accordingly, in the embodiment, in the period after the wafer alignmentoperation until before the beginning of exposure, a switching operationof the position measurement system has to be performed, in which theposition measurement system used for measuring the position of the waferstage is switched from wafer interferometer system 18 (that is, wafer Yinterferometer 18Y and wafer X interferometer 18X₂) to encoders 50A to50D.

The switching operation of the position measurement system will now bebriefly described in the description below.

At the point when wafer alignment has been completed, the position ofwafer stage WST is controlled by main controller 20, based on themeasurement values of interferometers 18Y, 18X₂, 18Z₁, and 18Z₂ as isshown, for example, in FIG. 7. Therefore, after wafer alignment has beencompleted, main controller 20 drives wafer stage WST in the +Y directionvia wafer stage drive system 27, based on the measurement values ofthese interferometers 18Y, 18X₂, 18Z₁, and 18Z₂.

Then, when wafer stage WST reaches a position where the two measurementbeams from interferometer 18X₂ and 18X₁ irradiate X movable mirror 17Xat the same time, as is shown in FIG. 8, main controller 20 presets themeasurement values of interferometer 18X₁ to the same values as themeasurement values of interferometer 18X₂, after adjusting the attitudeof wafer stage WST so that the θz rotation error (yawing error) (and theθx rotation error (pitching error)) becomes zero based on themeasurement values of interferometer 18Y. The θz rotation error of waferstage WST can also be adjusted, based on the measurement values of Zinterferometers 18Z₁ and 18Z₂.

Then, after the preset, main controller 20 suspends wafer stage WST atthe position for a predetermined time until the short-term variationcaused by air fluctuation (temperature fluctuation of air) ofinterferometers 18X₁ and 18Y falls to a level that can be ignored due toan averaging effect, and then carries over an addition average value(average value during the suspension time) of measurement values ofinterferometer 18X₁ obtained during the suspension of wafer stage WST asthe measurement values of X linear encoders 50B and 50D. Along with thisoperation, main controller 20 carries over addition average values(average value during the suspension time) of measurement values of theplurality of axes of interferometer 18Y obtained during the suspensionas the measurement values of Y linear encoders 50A and 50C. With thisoperation, preset of X linear encoders 50B and 50D and Y linear encoders50A and 50C, that is, the switching operation of the positionmeasurement system, is completed. Thus, hereinafter, main controller 20controls the position of wafer stage WST based on the measurement valuesof encoder 50A to 50D.

Scanning operation of reticle stage RST for exposure will be describednext, including the switching operation (linking the measurement values)of the encoders in the encoder system for the reticle stage.

For example, in the case of scanning exposure by the movement of wafer Win the +Y direction and the movement of reticle R1 in the −Y direction(to be referred to here as a plus scan exposure focusing on the movementdirection of wafer W), acceleration of reticle stage RST in the −Ydirection begins from the acceleration starting position shown in FIG.9. At this acceleration starting position, the position of reticle stageRST is measured by main controller 20 using encoders 26A₂, 26B₂, and26C₂.

Then, at the point of acceleration finishing when the acceleration ofreticle stage RST in the −Y direction has been completed, as an example,the −Y edge of reticle R1 substantially coincides with the +Y edge ofillumination area IAR, as is shown in FIG. 10. And, immediately beforethis, heads 26A₁, 26B₁, and 26C₁ move so that heads 26A₁, 26B₁, and 26C₁face movement scales 24A, 24B, and 28, respectively. That is, it becomespossible to measure the position of reticle stage RST not only withencoders 26A₂, 26B₂, and 26C₂, but also with 26A₁, 26B₁, and 26C₁.

Therefore, the measurement values of encoders 26A₂, 26B₂, and 26C₂(count values whose predetermined origin is zero (scale reading values))at some point from the point where the position of reticle stage RSTbecomes measurable using encoders 26A₁, 26B₁, and 26C₁ until the pointwhere acceleration has been completed, is succeeded without any changesby main controller 20 as measurement values of 26A₁, 26B₁, and 26C₁.Hereinafter, main controller 20 uses encoders 26A₁, 26B₁, and 26C₁ tocontrol the position of reticle stage RST.

Then, from the point shown in FIG. 10, reticle stage RST begins movementat a constant speed, and when the pattern area of reticle R1 reachesillumination area IAR after a predetermined settling time has passed,exposure begins (refer to FIG. 16). Furthermore, after a predeterminedperiod of time has passed, exposure is completed (refer to FIG. 17) anddeceleration of reticle stage RST begins, and reticle stage RST stops atthe position shown in FIG. 11. Incidentally, the deceleration of reticlestage RST can begin almost at the same time as the completion ofexposure.

As is obvious from FIGS. 10 and 11, during the period from before thebeginning of exposure (that is, the point where the switching of theencoders used for controlling the position of reticle stage RST has beenperformed) through the scanning exposure period until the decelerationhas been completed, the position of reticle stage RST is controlled bymain controller 20, based on the measurement values of encoders 26A₁,26B₁, and 26C₁.

Meanwhile, in the case of scanning exposure by the movement of wafer Win the −Y direction and the movement of reticle R1 in the +Y direction(a minus scan exposure), opposite to the plus scan exposure describedabove, acceleration of reticle stage RST in the +Y direction begins fromthe state shown in FIG. 11. Then, at the point shown in FIG. 10 whereexposure has been completed, the switching operation (linking themeasurement values) of the encoders is performed, and during thedeceleration period, the position of reticle stage RST is controlled bymain controller 20, based on the measurement values of encoders 26A₂,26B₂, and 26C₂.

In FIGS. 9, 10, 11 and the like, the state is shown where the positionof reticle stage RST is measured using interferometers 16 x and 16 y inaddition to the encoders, however, it is a matter of course that theposition measurement of reticle stage RST does not necessarily have tobe performed with the interferometers. The method of using themeasurement results of the encoders and interferometers 16 x and 16 yobtained during scanning exposure in the embodiment will be described,later in the description.

Although a detailed description will be omitted, in the plus scanexposure and minus scan exposure that use reticle R2, encoders 26A₁,26B₁, and 26C₁ and encoders 26A₃, 26B₃, and 26C₃ are used. The switchingoperation (linking the measurement values) similar to the descriptionabove is performed on these exposures as well, and at least during thescanning exposure, the position of reticle stage RST is controlled bymain controller 20 based on the measurement values of encoders 26A₁,26B₁, and 26C₁. Further, as well as the X, Y positions of reticle stageRST, main controller 20 also controls the position of reticle stage RSTin the θz direction (yawing), based on the measurement values of theencoder.

In exposure apparatus 100 of the embodiment, a series of operations suchas reticle alignment (includes making the reticle coordinate system andthe wafer coordinate system correspond with each other), baselinealignment of alignment system ALG and the like are performed, usingreticle alignment systems 13A and 13B (FIG. 6), the fiducial mark plateon wafer stage WST, alignment system ALG and the like, as in a typicalscanning stepper. The position control of reticle stage RST and waferstage WST during the series of operations is performed based on themeasurement values of interferometers 16 y and 16 x, and interferometers18X₁, 18X₂, 18Y, 18Z₁, and 18Z₂. In the reticle alignment or thebaseline measurement, the position control of reticle stage RST andwafer stage WST can be performed based on only the measurement values ofthe encoders described earlier, or on the measurement values of both theinterferometers and the encoders.

Next, wafer exchange of the wafer on wafer stage WST (in the case nowafers are on wafer stage WST, wafer loading is performed) is performedby main controller 20, using a wafer loader (not shown) (carrier unit),and then, wafer alignment is performed, for example, by the EGA method,using alignment system ALG. And according to this wafer alignment, thearrangement coordinates of the plurality of shot areas on the wafer onthe alignment coordinate system previously described can be obtained.

Then, main controller 20 performs the switching of the positionmeasurement system previously described, and then, main controller 20controls the position of wafer stage WST based on the measurement valuesof the baseline and the encoders 50A to 50D measured earlier, and in theprocedure similar to a typical scanning stepper, main controller 20performs exposure by the step and scan method, and the pattern of thereticle (R1 or R2) is transferred onto each of the plurality of shotareas on the wafer.

FIG. 12A shows a state in which wafer stage WST is located at a positionwhere the center of wafer W is positioned directly below projection unitPU, and FIG. 12B shows a state in which wafer stage WST is located at aposition where the area around the middle in between the center of waferW and its circumference is positioned directly below projection unit PU.Further, FIG. 13A shows a state in which wafer stage WST is located at aposition where the area close to the edge of wafer W on the +Y side ispositioned directly below projection unit PU, and FIG. 13B shows a statein which wafer stage WST is located at a position where the area closeto the edge of wafer W in the direction at an angle of 45 degrees withrespect to the X-axis and the Y-axis when viewed from the center ofwafer W is positioned directly below projection unit PU. Further, FIG.14 shows a state in which wafer stage WST is located at a position wherethe area close to the edge of wafer W on the +X side is positioneddirectly below projection unit PU. When viewing FIGS. 12A to 14, it canbe seen that in each drawing, at least one (in the embodiment, one ortwo) of the eleven heads in each of the head units 46A to 46D faces itscorresponding movement scale. And, when totally considering this fact,the symmetric arrangement of head units 46A to 46D vertically andhorizontally with optical axis AX of projection optical system PLserving as the center, and the symmetric arrangement of movement scales44A to 44D in the X-axis direction and Y-axis direction with respect tothe center of wafer stage WST, the following is obvious; that is, inexposure apparatus 100, no matter at which position wafer stage WST islocated within the movement range of wafer stage WST during scanningexposure, at least one of the eleven heads in each of the head units 46Ato 46D faces its corresponding movement scale, and the X position andthe Y position of wafer stage WST can be constantly measured accordingto the four encoders 50A to 50D. Further, yawing of wafer stage WST canalso be measured.

In other words, the four movement scales 44A to 44D are each set longerthan the size (diameter) of wafer W in the longitudinal direction, sothat the length in the longitudinal direction (corresponding to theformation range of the diffraction grating) covers the entire area ofthe movement strokes of (movement range) of wafer stage WST when atleast performing scanning exposure on the entire surface of wafer W (inthe embodiment, the four head units 46A to 46D (measurement beams) donot move off the corresponding movement scales (diffraction gratings) inall the shot areas at least during scanning exposure, during theacceleration/deceleration time of wafer stage WST before and after thescanning exposure, and during the synchronous settling time, that is,avoid becoming unmeasurable).

Further, the four head units 46A to 46D are each similarly set aroundthe same level or longer than the movement strokes in the longitudinaldirection, so that the length in the longitudinal direction(corresponding to the formation range of the diffraction grating) coversthe entire area of the movement strokes of wafer stage WST when at leastperforming scanning exposure on the entire surface of wafer W (that is,at least during exposure operation of wafer W, the four head units 46Ato 46D (measurement beams) do not move off the corresponding movementscales (diffraction gratings) at least during scanning exposure, thatis, avoid becoming unmeasurable). Incidentally, head units 46A to 46Dcan be configured so that they can measure the position of wafer stageWST according to encoders 50A to 50D not only during the exposureoperation, but also during other operations such as the alignmentoperation (including wafer alignment and baseline measurement, whichwere previously described).

In the movement scale of the encoder, the fixed position of the movementscale shifts due to the passage of use time, or the pitch of thediffraction grating changes partially or entirely due to thermalexpansion and the like, which makes the encoder lack in long-termstability. Therefore, the errors included in the measurement valuesbecome larger due to the passage of use time, and calibration becomesnecessary. In the description below, calibration operation of theencoders, which is performed in exposure apparatus 100 of theembodiment, will be described.

First of all, a first calibration operation for correcting gain errorsand linearity errors of the measurement values of the encodersconfiguring the encoder system for the reticle stage will be described.Since the first calibration operation is performed, for example, pereach lot before beginning the exposure of the first wafer, that is,performed at a relatively long interval, it will also be referred to asa long-term calibration in the description below.

More specifically, main controller 20 scans the range where illuminationarea IAR passes (it actually is the range where (the pattern areas of)reticles R1 and R2 move across illumination area IAR) reticles R1 and R2(their pattern areas) at an extremely slow speed at a level in which theshort-term variation of the measurement values of the interferometerscan be ignored, while moving reticle stage RST in the Y-axis direction.During this first calibration operation, illumination area IAR is notnecessarily illuminated with illumination light IL, however, in thiscase, in order to describe the movement position of reticle stage RST ina clearly understandable manner, the expressions such as “illuminationarea IAR passes” and the like are used.

During the scanning above, main controller 20 takes in the measurementvalues of reticle Y interferometer 16 y, Y linear encoders 26A₁ and26B₁, reticle X interferometer 16 x, and X linear encoders 26C₁ at apredetermined sampling interval, and stores the measurement values in amemory (not shown), and also makes a map as in FIG. 15 on themeasurement values of Y linear encoders 26A₁ and 26B₁ and measurementvalues of reticle Y interferometer 16 y, and on the measurement valuesof reticle X interferometer 16 x and the measurement values of X linearencoders 26C₁, respectively. The reason for taking in the measurementvalues of the three encoders 26A₁, 26B₁, and 26C₁ is due to taking intoconsideration the point in which the position of reticle stage RST iscontrolled using the three encoders 26A₁, 26B₁, and 26C₁ in the rangewhere illumination area IAR passes reticles R1 and R2 (their patternareas).

FIG. 15 is a line map that shows a curve C, which shows a relationbetween the measurement values of an interferometer and the measurementvalues of an encoder in the case the horizontal axis is the measurementvalues of the interferometer and the vertical axis is the measurementvalues of the encoder, and the difference between this curve C and anideal line TL indicates the errors included in the measurement values ofthe encoder. The line map in FIG. 15 can serve as a correction map forcorrecting the measurement values of the encoder without any changes.The reason for this is because, for example, in FIG. 15, point P1indicates that when the measurement value of the encoder is e1 themeasurement value of the corresponding interferometer is i1, and sincethis measurement value of the interferometer is a value which wasobtained when reticle stage RST was scanned at an extremely slow speedas is previously described, it is safe to say that this value naturallycontains no long-term variation errors as well as almost no short-termvariation errors due to air fluctuation, and that it is an accuratevalue in which errors can be ignored.

When the relation between the measurement values after correction ofencoders 26A₁, 26B₁, and 26C₁ whose measurement values have beencorrected according to the correction map of FIG. 15 and thecorresponding interferometers is obtained, the relation coincides withideal line TL in FIG. 15. The correction map for correcting themeasurement values of encoder 26C₁ can naturally be made based on themeasurement values of encoder 26C₁ and reticle X interferometer 16 x,which are obtained while driving reticle stage RST in the X-axisdirection within a movable range.

Main controller 20 can also make correction maps for the remainingencoders, using the measurement values of interferometers 16 x and 16 yin a procedure similar to encoders 26A₁, 26B₁, and 26C₁ described above.

However, besides the long-term calibration operation described above, inthe case of also performing together a short-term calibration operationwhich will be described later, curve C of the correction map above canbe separated into a low order component, which is an offset componentand a gradient component, and a high order component that is a componentbesides the low order component, and a correction map can be kept forboth the low order component and the high order component, or the loworder component can further be separated into the offset component andthe gradient component and a correction map can be kept for both theoffset component and the gradient component, along with the correctionmap of the high order component. Or, a correction map (correctioninformation) on the high order component which is expected to beimmovable for a relatively long period can be kept, and the correctioninformation of the low order component which is expected to change in arelatively short period can be obtained by the short-term calibrationoperation.

In the description above, in the calibration operation of obtaining(deciding) the correction information of the measurement values of atleast encoders 26A₁ and 26B₁, reticle stage RST was moved in thescanning direction (the Y-axis direction) in a range where the patternareas of reticle R1 and R2 move across illumination area IAR, however,the movement range of reticle stage RST is not limited to this. Forexample, the movement range can substantially be the entire measurablerange (corresponds to the formation range of the diffraction grating ofmovement scales 24A and 24B) of encoders 26A₁ and 26B₁, or the movementrange during the scanning exposure using one of the reticles R1 and R2.The movement range during the scanning exposure can be a movement rangenot only during the scanning exposure, but can also include the movementrange in at least a part of the time of acceleration/deceleration beforeand after the scanning exposure and the synchronous settling time.Further, the movement range of reticle stage RST is not limited to themovement range of reticle stage RST during scanning exposure that usesreticles R1 and R2, and can include the movement range during themeasurement operation using the a reference mark (not shown) arranged onreticle stage RST. The reference mark can be at least one mark arrangedon reticle stage RST on the −Y side with respect to reticle R1 and/or onthe +Y side with respect to reticle R2.

Next, a second calibration operation for calibrating a gain error (ascaling error of an encoder measurement value to an interferometermeasurement value) in encoders 26A₁, 26B₁, and 26C₁ which is performed,for example, per each wafer (during a so-called overhead time (theperiod after completing the exposure of a wafer until the beginning ofexposure of the next wafer)), will be described. Since the secondcalibration operation is performed for each wafer, that is, is performedat a relatively short interval, this operation will also be referred toas a short-term calibration in the description below.

First of all, as is shown in FIG. 16, main controller 20 sets theposition of reticle stage RST in the scanning direction (the Y-axisdirection) to a first Y position (hereinafter also simply referred to asa first position) so that the edge section on the −Y side of the patternarea of reticle R1 (or R2) used in the next exposure coincides with theedge section on the +Y side of illumination area IAR. On thiscalibration operation as well, illumination area IAR is not necessarilyilluminated with illumination light IL, however, in FIG. 16,illumination area IAR is indicated in order to make the position ofreticle stage RST easier to understand.

Then, main controller 20 continues the position setting state at thefirst position above shown in FIG. 16 for a predetermined period oftime, and while continuing this state, obtains the measurement values ofencoders 26A₁, 26B₁, and 26C₁ and interferometers 16 x and 16 y at apredetermined sampling interval, and stores the measurement values inmemory (not shown).

Next, main controller 20 drives reticle stage RST in the −Y direction,and as is shown in FIG. 17, sets the position of reticle stage RST to asecond Y position (hereinafter also simply referred to as a secondposition) so that the edge section on the +Y side of the pattern area ofreticle R1 (or R2) coincides with the edge section on the −Y side ofillumination area IAR. Then, main controller 20 continues the positionsetting state at the second position above shown in FIG. 17 for apredetermined period of time, and while continuing this state, obtainsthe measurement values of encoders 26A₁, 26B₁, and 26C₁ andinterferometers 16 x and 16 y at a predetermined sampling interval, andstores the measurement values in memory (not shown).

Then, based on the measurement values (information) stored in memory ateach of the first and second positions above, main controller 20computes the averaging value (time averaging value) of the measurementvalues at each of the first and the second positions described above,for encoders 26A₁, 26B₁, and 26C₁ and interferometers 16 x and 16 y.Then, based on the computed results, main controller 20 makes a map onthe measurement values of Y linear encoders 26A₁ and 26B₁ and themeasurement values of reticle Y interferometer 16 y, and also on themeasurement values of reticle X interferometer 16 x and X linear encoder26C₁, like the one shown in FIG. 18. In the map in FIG. 18, point P2 andpoint P3 are points that show the relation between the measurementvalues of the interferometers at each of the first and second positionswhose short-term variation due to air fluctuation or the like is reducedby the averaging effect and the measurement values of the correspondingencoders.

Next, main controller 20 computes a gradient component (scaling) S_(c)of a correction map used for correcting the measurement values of theencoder using the measurement values of the interferometer from thefollowing equation.

S _(c)=(e3−e2)/(i3−i2)

Then, main controller 20 replaces the gradient component of thecorrection map that has been computed with the gradient component in thecorrection map of the low order component. And based on the correctionmap of the low order component that has been replaced and the high ordercomponent kept as the correction map, main controller 20 makes a newcorrection map for correcting the low order component and the high ordercomponent.

In the description above, the position of reticle stage RST was set toboth the first position and the second position, which are the positionson both edges of the range where illumination area IAR passes thepattern area of reticles R1 and R2, and a predetermined processing wasperformed so as to compute the new correction information describedabove. However, the computation is not limited to this, and the positionof reticle stage RST can be set besides the first position and thesecond position, to three or more positions which include at least oneposition between the first position and the second position. And then,the processing similar to the description above is performed, and aleast squares approximation straight line of the three or more pointsthat have been obtained can be computed, and based on the approximationstraight line, an offset component can also be computed in addition tothe gradient component of the correction map (scaling error). In thiscase, a new correction map for correcting the low order component andthe high order component can be made, based on the low order componentof the correction map that has been computed (gradient component andoffset component) and the high order component kept as the correctionmap. Further, the first and second positions to which the position ofreticle stage RST is set was made to correspond to both edges of themovement range of reticle stage RST so that the entire pattern area ofthe reticle moves across illumination area IAR in the scanningdirection. However, the present invention is not limited to this, andfor example, the position of reticle stage RST can be made to correspondto the actual movement range (the movement range including the time ofacceleration/deceleration before and after the scanning exposure and thesynchronous settling time) of reticle stage RST during scanning exposureusing one of the reticles R1 and R2. Furthermore, a part of the movementrange in the scanning direction set by the first and second positionscan be shifted from the movement range of reticle stage RST for theentire pattern area of the reticle to move across illumination area IAR,however, it is preferable for the movement range set by the first andsecond positions to include the movement range of reticle stage RST forthe entire pattern area of the reticle to move across illumination areaIAR. Further, the movement range of reticle stage RST can include themovement range during measurement operation using the reference marks.

Next, a third calibration operation performed per wafer (the so-calledoverhead time) for revising a gain error (a scaling error and an offsetof an encoder measurement value to an interferometer measurement value)in encoders 26A₁, 26B₁, and 26C₁, that is, the low order component ofthe correction map described earlier, will be described. This thirdcalibration operation will also be referred to as a short-termcalibration below, due to the same reasons as before.

First of all, main controller 20 drives reticle stage RST in the Y-axisdirection within a predetermined range in which illumination area IARpasses the pattern area of reticle R1 (or R2) used in the next exposure.Reticle stage RST is driven at a low speed, but at a level in which thethroughput can be maintained within an allowable range even if thethroughput of exposure apparatus 100 decreases due to performing thethird calibration operation. Then, during the drive, main controller 20obtains the positional information of reticle stage RST at apredetermined sampling interval using interferometers 16 x and 16 y andencoders 26A₁, 26B₁, and 26C₁, and stores the measurement values inmemory (not shown). Also on this third calibration, illumination areaIAR is not necessarily illuminated with illumination light IL, however,for the same reasons as before, the expressions such as “illuminationarea IAR passes” and the like are used. Further, the movement range ofreticle stage RST is the same range as the range described in the secondcalibration operation. However, in the third calibration operation,position setting of reticle stage RST does not have to be performed atboth edges of the movement range.

Then, main controller 20 makes a curve as in a curve C1 shown in FIG. 19for each of the measurement values of Y linear encoders 26A₁ and 26B₁and the measurement values of reticle Y interferometer 16 y, and themeasurement values of reticle X interferometer 16 x and the measurementvalues of X linear encoder 26C₁, in a similar manner as in the previousdescription. In FIG. 19, reference code EA indicates the predeterminedrange in which illumination area IAR passes the pattern area of reticleR1 (or R2), that is, the exposure section.

Next, main controller 20 obtains a least squares approximation straightline FL of curve C1, and then obtains an offset drift OD and a scalingdrift SD of approximation straight line FL to ideal line TL. Then, usingoffset drift (offset error) and scaling drift (gradient error) that havebeen obtained, the correction map of the low order component kept inadvance as a map is revised. Then, based on the correction map of thelow order component that has been corrected and the correction map ofthe high order component kept in advance as a map, main controller 20makes a new correction map for correcting the low order component andthe high order component.

At least a part of the movement range of reticle stage RST in the thirdcalibration operation can be shifted from a predetermined range(corresponding to exposure section EA) for the entire pattern area ofthe reticle to move across illumination area IAR, however, it ispreferable for the movement range to include the predetermine range, andfor example, the movement range can be the actual moving range ofreticle stage RST during scanning exposure (the movement range thatincludes the acceleration/deceleration and synchronous settling periodbefore and after the scanning exposure) using one of reticles R1 and R2.Further, the movement range of reticle stage RST can include themovement range during measurement operation using the reference markspreviously described.

In exposure apparatus 100, main controller 20 performs the long-termcalibration operation and the short-term calibration operation forencoders 50A to 50D used for controlling the position of wafer stage WSTduring the exposure operation in a similar method as in the first tothird calibration previously described. However, wafer stage WST moveswithin a two-dimensional plane. In this case, main controller 20 driveswafer stage WST on an orthogonal coordinate system set by wafer Yinterferometer 18Y and wafer X interferometer 18X₁ and obtains acorrection map based on errors of the measurement values of X linearencoders 50B and 50D, as well as a correction map based on errors of themeasurement values of Y linear encoders 50A and 50C. In this case, thedisposal direction of the diffraction grating of movement scales 44A and44C Y and the longitudinal direction of linear encoders 50A and 50C areboth in the Y-axis direction, and the longitudinal direction of headunits 46A and 46C (the disposal direction of the heads) is in the X-axisdirection.

Next, the long-term calibration operation (the first calibrationoperation) of encoders 50A to 50 D performed in exposure apparatus 100of the embodiment, that is, an acquisition operation of correctioninformation of the grating pitch of the movement scales and correctioninformation of grating deformation of wafer stage WST will be described,based on FIG. 20.

In FIG. 20, measurement beams B4 ₁ and B4 ₂ from Y interferometer 18Yare placed symmetrically to a straight line (coincides with a straightline formed when the center of a plurality of heads of head unit 46B andhead unit 46D are joined) parallel to the Y-axis that passes through theoptical axis of projection optical system PL, and the substantialmeasurement axis of Y interferometer 18Y coincides with a straight lineparallel with the Y-axis that passes through the optical axis ofprojection optical system PL. Therefore, according to Y interferometer18Y, the Y position of wafer stage WST can be measured without Abbeerrors. Similarly, the measurement beam from X interferometer 18X₁ isplaced on a straight line (coincides with a straight line formed whenthe center of a plurality of heads of head unit 46A and head unit 46Care joined) parallel to the X-axis that passes through the optical axisof projection optical system PL, and the measurement axis of Xinterferometer 18X₁ coincides with a straight line parallel with theX-axis that passes through the optical axis of projection optical systemPL. Therefore, according to X interferometer 18X₁, the X position ofwafer stage WST can be measured without Abbe errors.

Now, as an example, an acquisition operation of correction informationof deformation of the grating lines (grating line warp) of the X scaleand the correction information of the grating pitch of the Y scale willbe described. In order to simplify the description, the reflectionsurface of movable mirror 17X is to be an ideal plane.

First of all, main controller 20 drives wafer stage WST based on themeasurement values of Y interferometer 18Y, X interferometer 18X₁, and Zinterferometers 18Z₁ and 18Z₂, and sets the position of wafer stage WSTas is shown in FIG. 20 so that movement scales 44A and 44C are placeddirectly under the corresponding head units 46A and 46C (at least onehead) and the edge on the +Y side of movement scales (diffractiongratings) 44A and 44C each coincide with the corresponding head units46A and 46C.

Next, main controller 20 moves wafer stage WST in the +Y direction, forexample, until the other end (the edge on the −Y side) of movementscales 44A and 44C coincides with the corresponding head units 46A and46C as is indicated by an arrow F in FIG. 20 in a low speed at a levelin which the short-term variation of the measurement values of Yinterferometer 18Y can be ignored and also with the measurement valuesof X interferometer 18X₁ fixed at a predetermined value, based on themeasurement values of Y interferometer 18Y and Z interferometers 18Z₁and 18Z₂ while maintaining all of the pitching amount, rolling amount,and yawing amount at zero. During this movement, main controller 20takes in the measurement values of Y linear encoders 50A and 50C and themeasurement values of Y interferometer 18Y (measurement values accordingto measurement beams B4 ₁ and B4 ₂) at a predetermined samplinginterval, and then obtains the relation between the measurement valuesof Y linear encoders 50A and 50C and the measurement values of Yinterferometer 18Y, based on the measurement values that are taken in.More specifically, main controller 20 obtains the grating pitch (thedistance between adjacent grating lines) of movement scales 44A and 44C,which are placed sequentially facing head units 46A and 46C along withthe movement of wafer stage WST and the correction information of thegrating pitch. The correction information of the grating pitch can beobtained, for example, in the case the horizontal axis indicates themeasurement values of the interferometer and the vertical axis indicatesthe measurement values of the encoders, as a correction map or the likethat denotes a relation between the two using a curve. Since themeasurement values of Y interferometer 18 in this case are values whichcan be obtained when wafer stage WST was scanned at an extremely slowspeed as is previously described, it is safe to say that these valuesnaturally contain no long-term variation errors as well as almost noshort-term variation errors due to air fluctuation, and that it is anaccurate value in which errors can be ignored. In this case, wafer stageWST was driven in the Y-axis direction covering a range in which bothedges of movement scales 44A and 44C move across the corresponding headunits 46A and 46C. The movement range, however, is not limited to this,and for example, wafer stage WST can be driven in a range in the Y-axisdirection in which wafer stage WST is moved during exposure operation ofa wafer.

Further, during the movement of wafer stage WST, by statisticallyprocessing the measurement values (measurement values of X linearencoders 50B and 50D) obtained from the plurality of heads of head units46B and 46D, which are sequentially placed facing movement scales 44Band 44D along with the movement of wafer stage WST, such as for example,by averaging (or weighted averaging), main controller 20 also obtainscorrection information of the deformation (warp) of the grating linesthat sequentially face the plurality of heads. This is because in thecase the reflection surface of movable mirror 17X is an ideal plane, thesame variation pattern should repeatedly appear during the process ofsending wafer stage WST in the +Y direction, therefore, if themeasurement data obtained by the plurality of heads is averaged, thecorrection information of the deformation (warp) of the grating lines ofmovement scales 44B and 44D that sequentially face the plurality ofheads can be accurately obtained.

In the case the reflection surface of movable mirror 17X is not an idealplane, the unevenness (distortion) of the reflection surface is to bemeasured and correction data of the distortion is to be obtained. Then,on the movement of wafer stage WST in the +Y direction described above,instead of fixing the measurement value of X interferometer 18X₁ to apredetermined value, by controlling the X position of wafer stage WSTbased on the correction data, wafer stage WST can be accurately moved inthe Y-axis direction. When this operation is applied, the correctioninformation of the grating pitch of movement scales 44A and 44C and thecorrection information of the deformation (warp) of the grating lines ofmovement scales 44B and 44D can be accurately obtained in completely thesame manner as in the above description. The measurement data obtainedusing the plurality of heads of head units 46B and 46D is a plurality ofdata at different regions of reference on the reflection surface ofmovable mirror 17X, and the heads each measure the deformation (warp) ofthe same grating line. Therefore, by the averaging or the like describedabove, an incidental effect occurs in which the distortion correctionresidual of the reflection surface is averaged so that it becomes closerto a true value (in other words, by averaging the measurement data (warpinformation of the grating line) obtained by a plurality of heads, theinfluence of the distortion residual can be reduced).

Since only the disposal direction of the diffraction grating, thelongitudinal direction of movement scales 44B and 44D, and thelongitudinal direction of head units 46B and 46D (the disposal directionof the heads) in X linear encoders 50B and 50D are opposite in theX-axis and Y-axis direction to the Y linear encoders 50A and 50C,details on the acquisition operation (the first calibration operation)of the correction information of the deformation (warp) of the gratinglines of the Y scale and the correction information of the grating pitchof movement scales 50B and 50D will be omitted because the processingthat needs to be performed is the correction described above with theX-axis direction and Y-axis direction interchanged.

As in the description above, main controller 20 obtains the correctioninformation of the grating pitch of movement scales 44A and 44C, thecorrection information of the deformation (warp) of the grating lines ofmovement scales 44B and 44D, the correction information of the gratingpitch of movement scales 44B and 44D and the correction information ofthe deformation (warp) of the grating lines of movement scales 44A and44C, per a predetermined timing, such as for example, for each lot.

Then, during the exposure processing or the like of the wafer in thelot, main controller 20 performs position control of wafer stage WST inthe Y-axis direction while correcting the measurement values (that is,the measurement values of encoders 50A and 50C) obtained from head units46A and 46C based on the correction information of the grating pitch andthe correction information of the deformation (warp) of the gratinglines of movement scales 44A and 44C. Accordingly, it becomes possiblefor main controller 20 to perform position control of wafer stage WST inthe Y-axis direction with good accuracy using linear encoders 50A and50C, without being affected by the influence of the temporal change ofthe grating pitch and the grating line warp of movement scales 44A and44C.

Further, during the exposure processing or the like of the wafer in thelot, main controller 20 performs position control of wafer stage WST inthe X-axis direction while correcting the measurement values (that is,the measurement values of encoders 50B and 50D) obtained from head units46B and 46D based on the correction information of the grating pitch andthe correction information of the deformation (warp) of the gratinglines of movement scales 44B and 44D. Accordingly, it becomes possiblefor main controller 20 to perform position control of wafer stage WST inthe X-axis direction with good accuracy using linear encoders 50B and50D, without being affected by the influence of the temporal change ofthe grating pitch and the grating line warp of movement scales 44B and44D.

In the description above, the correction information of the gratingpitch and the deformation (warp) of the grating lines were obtained foreach of the movement scales 44A to 44D, however, the present inventionis not limited to this, and the correction information of the gratingpitch and the deformation (warp) of the grating lines can be obtainedfor only one of movement scales 44A and 44C and movement scales 44B and44D, or the correction information of only one of the grating pitch andthe deformation (warp) of the grating lines can be obtained for bothmovement scales 44A and 44C and movement scales 44B and 44D.

Although a detailed description will be omitted, the short-termcalibration operation (the second and third calibration operations) ofencoders 50A to 50D used for controlling the position of wafer stage WSTduring the exposure operation is to be performed according to thelong-term calibration operation (the first calibration operation)described above.

Then, on the exposure operation by the step-and-scan method, maincontroller 20 performs position control of reticle stage RST based onthe measurement values of encoders 26A₁, 26B₁, and 26C₁ and theircorrection maps, as well as the position control of wafer stage WSTbased on the measurement values of encoders 50A to 50D and theircorrection maps.

Further, in exposure apparatus 100 of the embodiment, reticle R1 andreticle R2 can be simultaneously mounted on reticle stage RST.Therefore, by having completed reticle alignment of reticle R1 andreticle R2, main controller 20 can perform double exposure, for example,using reticle R1 and reticle R2, by simply moving reticle stage RSTbased on the measurement values of encoders 26A₁, 26B₁, and 26C₁ withoutperforming the reticle exchange operation to reticle stage RST.

The encoders used in the embodiment is not limited to the encoder by thediffraction interference method and encoders of various types of methodscan be used, such as an encoder by the so-called pick up method, or forexample, a so-called scan encoder whose details are disclosed in, forexample, U.S. Pat. No. 6,639,686 or the like.

As is described in detail above, according to exposure apparatus 100related to the embodiment, main controller 20 performs calibrationoperation of, for example, encoders 26A₁, 26B₁, and 26C₁. Morespecifically, correction information for correcting measurement valuesof encoders 26A₁, 26B₁, and 26C₁ and the like whose short-term stabilityof the measurement values is superior to interferometers 16 y and 16 xare acquired, using the measurement values of interferometers 16 y and16 x whose linearity and long-term stability of the measurement valuesare superior to encoders 26A₁, 26B₁, and 26C₁. Then, main controller 20drives reticle stage RST during scanning exposure or the like, based onthe measurement values and the correction information of encoders 26A₁,26B₁, and 26C₁.

Accordingly, reticle stage RST can be driven with good precision, basedon the positional information of reticle stage RST whose linearity andlong-term stability is good in addition to the measurement values ofencoders 26A₁, 26B₁, and 26C₁ that have been corrected using thecorrection information, that is, the short-term stability.

Further, according to exposure apparatus 100, by the long-termcalibration previously described, correction information for correctingmeasurement values of encoders 26A₁ and 26B₁ whose short-term stabilityof the measurement values is superior to interferometer 16 y isacquired, using the measurement values of interferometer 16 y whoselinearity and long-term stability of the measurement values are superiorto encoders 26A₁ and 26B₁. Then, during pattern transfer or the like,main controller 20 controls the movement of reticle stage RST based onthe measurement values of encoders 26A₁ and 26B₁ and the correctioninformation. Accordingly, it becomes possible to control the movement ofreticle stage RST with good precision, based on the positionalinformation of reticle stage RST in the scanning direction whoselinearity and long-term stability is good in addition to the measurementvalues of encoders 26A₁ and 26B₁ that have been corrected using thecorrection information, that is, the short-term stability.

Further, according to exposure apparatus 100, by one of the short-termcalibrations previously described, correction information for correctinga low order component (scaling error, or a scaling error and a scalingoffset) of a map information that denotes a relation between themeasurement values of interferometer 16 y whose linearity and long-termstability of the measurement values are superior to encoders 26A₁ and26B₁ and the measurement values of encoders 26A₁ and 26B₁ whoseshort-term stability of the measurement values is superior tointerferometer 16 y is acquired. Then, during pattern transfer or thelike, main controller 20 controls the movement of reticle stage RST,based on the measurement values of encoders 26A₁ and 26B₁ and the mapinformation whose low order component has been corrected using thecorrection information obtained above.

Further, according to exposure apparatus 100, main controller 20performs calibration operation of, for example, encoders 50A to 50D inthe manner similar to the calibration operation of encoders 26A₁ and26B₁ described above. More specifically, correction information forcorrecting measurement values of encoders 50A to 50D whose short-termstability of the measurement values is superior to interferometers 18Yand 18X are acquired, using the measurement values of interferometers18Y and 18X whose linearity and long-term stability of the measurementvalues are superior to encoders 50A to 50D. Then, main controller 20drives wafer stage WST during scanning exposure, during the steppingmovement in between shot areas, and the like, based on the measurementvalues and the correction information of encoders 50A to 50D.

Accordingly, wafer stage WST can be driven with good precision in boththe X-axis and the Y-axis directions, based on the positionalinformation of wafer stage WST in the X-axis and the Y-axis directionswhose linearity and long-term stability is good in addition to themeasurement values of encoders 50A to 50D that have been corrected usingthe correction information, that is, the short-term stability.

Accordingly, with exposure apparatus 100 of the embodiment, on scanningexposure of each shot area on the wafer, main controller 20 can drivereticle R1 or R2 (reticle stage RST) and wafer W (wafer stage WST) inthe scanning direction (Y-axis direction) with good accuracy based onthe measurement values of encoders 26A₁, 26B₁, and 26C₁ and encoders 50Ato 50D, as well as perform position setting of reticle R1 or R2 (reticlestage RST) and wafer W (wafer stage WST) in the non-scanning direction(X-axis direction) with high precision. Accordingly, it becomes possibleto form the pattern of reticle R1 (or R2) on the plurality of shot areason wafer W with good accuracy.

In exposure apparatus 100 of the embodiment, main controller 20 revisedthe correction information of the measurement values of the encodersbased on the measurement values of the encoders and the interferometers,which were obtained by moving reticle stage RST separately from theexposure operation. However, for example, the correction information canbe revised, using the measurement values of the encoders and theinterferometers, which are obtained during the movement of reticle stageRST during the exposure operation. More specifically, when performingthe exposure operation by the step-and-scan method in which the patternof reticle R1 (or R2) is sequentially transferred on the plurality ofshot areas on wafer W, the position of reticle stage RST can becontrolled based on the measurement values of the encoders and thecorrection information, for example, during the scanning exposure ofeach shot area. And, in parallel with the control (exposure operation ofthe wafer), the measurement values of the interferometers and theencoders can be accumulated. Then, based on the accumulated measurementvalues, sequential calibration of measurement errors of the encoders inwhich the correction information (for example, a map information thatdenotes a relation between measurement values of the interferometers andthe measurement values of the encoders as is shown in FIG. 21) iscalibrated in prior to exposing the next wafer can be performed.

In FIG. 21, reference numeral C2 indicates the average value of theaccumulated data, and this data of the average value is an averaging ofthe short-term variation (variation in measurement values due to airfluctuation or the like) of the measurement values of theinterferometer. In this case, the data during scanning exposure does nothave to be accumulated for all the shot areas, and the data duringscanning exposure can merely be accumulated for the number of shot areasenough to perform the averaging of the short-term variation of themeasurement values of the interferometer. In FIG. 21, reference code EAindicates an exposure section as in FIG. 19.

In this case as well, when performing exposure operation of the nextwafer by the step-and-scan method, the movement of reticle stage RSTduring scanning exposure of each shot area can be controlled with goodprecision, based on the measurement values of the encoders correctedusing the correction information (for example, the map information inFIG. 21), that is, on the positional information of the reticle stagewhose linearity and long-term stability is good in addition to theshort-term stability. Accordingly, it becomes possible to transfer thepattern formed on reticle R1 (or R2) by scanning exposure on theplurality of shot areas on the wafer with good accuracy. The calibrationcan be performed not only on the Y linear encoders but also on the Xlinear encoders, or the calibration can further be preformed on theencoder system (encoders 50A to 50D) of the wafer stage.

In exposure apparatus 100 in the embodiment above, correctioninformation of the grating pitch of the movement scales and correctioninformation of grating deformation can be obtained by a method relatedto a modified example, which will be described below.

An acquisition operation of correction information of the grating pitchof movement scales 44A and 44C and correction information of deformation(warp of the grating lines) of the grating lines of movement scales 44Band 44D will now be described. Further, in order to make the descriptionsimple, the reflection surface of movable mirror 17X is to be an idealplane.

First of all, main controller 20 moves wafer stage WST, for example, inthe +Y direction indicated by an arrow F in FIG. 22 in the stroke rangepreviously described, while maintaining all of the pitching amount, therolling amount, and the yawing amount to zero, based on the measurementvalues of Y interferometer 18Y, and Z interferometers 18Z₁ and 18Z₂while fixing the measurement values of X interferometer 18X₁ to apredetermined value. During this movement, main controller 20 takes inthe measurement values of encoders 50A and 50C and the measurementvalues of Y interferometer Y18 (the measurement values according tomeasurement beams B4 ₁ and B4 ₂) into an internal memory at apredetermined sampling interval. In this case, the measurement values ofencoder 50C is obtained from head 48 k of head unit 46C, which isindicated enclosed in a circle in FIG. 22, located at a position adistance a away in the +X direction from a straight line LV parallel tothe Y-axis that passes through the optical axis of projection opticalsystem PL, facing movement scale 44C. Further, the measurement values ofencoder 50A is obtained from head 48 e of head unit 46A, which isindicated enclosed in a circle in FIG. 22, located at a position adistance b away in the −X direction from straight line LV, facingmovement scale 44A.

Next, after main controller 20 moves wafer stage WST in the +X directionby a predetermined distance based on the measurement values of Xinterferometer 18X₁, main controller 20 moves wafer stage WST in the −Ydirection indicated by an arrow F′ in FIG. 22 by a predetermineddistance based on the measurement values of Y interferometer 18Y, andthen makes wafer stage WST stop at this position.

Then, main controller 20 moves wafer stage WST, for example, in the +Ydirection indicated by an arrow F in FIG. 23 in the stroke rangepreviously described, while maintaining all of the pitching amount, therolling amount, and the yawing amount close to zero as much as possible,based on the measurement values of Y interferometer 18Y, and Zinterferometers 18Z₁ and 18Z₂ while fixing the measurement values of Xinterferometer 18X₁ to a predetermined value. During this movement, maincontroller 20 takes in the measurement values of encoders 50A and 50Cand the measurement values of Y interferometer Y18 (the measurementvalues according to measurement beams B4 ₁ and B4 ₂) into an internalmemory at a predetermined sampling interval. In this case, themeasurement values of encoder 50C is obtained from head 48 e of headunit 46C, which is indicated enclosed in a circle in FIG. 23, located ata position a distance b away in the +X direction from straight line LV,facing movement scale 44C. Further, the measurement values of encoder50A is obtained from head 48 k of head unit 46A, which is indicatedenclosed in a circle in FIG. 23, located at a position a distance a awayin the −X direction from straight line LV, facing movement scale 44A.

However, since the position of each head on the XY coordinate system isknown, by forming a simultaneous equation using the sampling valuesobtained in the two operations above and solving the simultaneousequation, the correction information (e.g. a correction map) of thegrating pitch of movement scales 44C and 44A can be respectivelyobtained independently.

In the case the reflection surface of movable mirror 17X is not an idealplane, the unevenness (distortion) of the reflection surface is to bemeasured and correction data of the distortion is to be obtained. Then,on the movement of wafer stage WST in the +Y direction shown in FIGS. 22and 23 described above, instead of fixing the measurement value of Xinterferometer 18X₁ to a predetermined value, by controlling the Xposition of wafer stage WST based on the correction data, wafer stageWST can be accurately moved in the Y-axis direction.

After the correction information (e.g. a correction map) of the gratingpitch of each of the movement scales 44C and 44A has been obtained inthe manner described above, main controller 20 then moves wafer stageWST in the +Y direction as is shown, for example, in FIG. 24, in aprocedure similar to the case in FIG. 22 or the like described above.This case is different, however, from when the correction information ofthe grating pitch of movement scales 44C and 44A was obtained, and head48 g of head unit 46B and head 48 i of head unit 46D that are indicatedenclosed in a circle in FIG. 24 facing movement scales 44B and 44D, arelocated away from the measurement axis of X interferometer 18X₁.Therefore, an apparent yawing amount of wafer stage WST measured by theinterferometer due to air fluctuation affects the measurement values ofencoders 50B and 50D (head 48 g of head unit 46B and head 48 i of headunit 46D), and is included in the measurement values as an error(hereinafter referred to shortly as a “yawing-induced error). However,in this case, the apparent yawing amount of wafer stage WST measured bythe interferometer due to the air fluctuation described above can bemeasured, using encoders 50A and 50C (head 48 h of head unit 46A andhead 48 h of head unit 46C enclosed in a circle in FIG. 24, facingmovement scales 44A and 44C). More specifically, while correcting themeasurement values of encoders 50A and 50C using the correctioninformation of the grating pitch of movement scales 44C and 44A that hasbeen obtained earlier, main controller 20 can obtain the apparent yawingamount of wafer stage WST described above, based on the measurementvalues that have been corrected. Then, main controller 20 can correctthe yawing-induced error described above, using the apparent yawingamount that has been obtained.

Main controller 20 moves wafer stage WST in the +Y direction, and duringthis movement, takes in the measurement values obtained from a pluralityof heads of head units 46B and 46D, which are sequentially placed facingmovement scales 44B and 44D, into an internal memory at a predeterminedsampling interval while correcting the yawing-induced error in themanner described above. Then, for the same reasons described earlier,main controller 20 performs statistical processing on the measurementvalues taken in the internal memory, such as for example, averaging (orweighted averaging) so that the correction information of thedeformation (warp) of the grating lines of movement scales 44B and 44Dcan also be obtained.

Further, also in the case of obtaining the correction information (e.g.correction map) of the grating pitch of movement scales 44A and 44Cand/or the correction information of the deformation (warp) of thegrating lines of movement scales 44B and 44D by driving wafer stage WSTin the −Y direction indicated by arrow F′ in FIGS. 22, 23, and 24 takinginto consideration the reciprocal difference, the processing similar tothe description above should be performed.

Meanwhile, on obtaining the correction information of the deformation(warp) of the grating lines of movement scales 44A and 44C and thecorrection information of the grating pitch of movement scales 44B and44D, main controller 20 performs the same processing described abovewith the X-axis direction and the Y-axis direction interchanged. Detailson this will be omitted.

Since each scale (diffraction grating) has a width, on obtaining thecorrection information, the correction information of the grating pitchcan be obtained, for example, by obtaining the correction informationabove along three lines in the width direction, on the right, left, andin the center, and as for the correction information of the grating linewarp, a grating line can be representatively chosen so as to measure thewarp. This is preferable, from the viewpoint of accuracy andworkability.

According to the method related to the modified example described above,when obtaining the correction information of the grating pitch and/orthe correction information of the deformation of the grating lines (warpof the grating lines), wafer stage WST does not necessarily have to bemoved at an extremely low speed. Therefore, it becomes possible toperform the acquisition operation of such correction informationdescribed above in a short time.

Next, a modified example of an encoder system for the wafer stage willbe described, referring to FIGS. 25 and 26. In FIGS. 25 and 26, the onlypoint different from FIG. 3 is the configuration of the encoder system,therefore, in the description below, for parts that have the same orsimilar arrangement as in FIG. 3, the same reference numerals will beused, and the description thereabout will be omitted.

As is shown in FIG. 25, on the upper surface of wafer stage WST, twomovement scales 52A and 52B whose longitudinal direction are orthogonalto each other and the longitudinal direction is the Y-axis direction andthe X-axis direction, respectively, are fixed in an L-shape. On thesurface of the two movement scales 52A and 52B, a reflection typediffraction grating that has a period direction orthogonal to thelongitudinal direction is formed.

Further, head unit 46A and a pair of head units 46B₁ and 46B₂ are eachplaced crossing the corresponding movement scales 52A and 52B, and arefixed to barrel platform 38 in a suspended state via a support member(not shown). Head unit 46A is placed on an axis (center axis) parallelto the X-axis that passes through optical axis AX of projection opticalsystem PL with the longitudinal direction (the disposal direction of theheads) being the X-axis direction (the period direction of thediffraction grating), which is orthogonal to the longitudinal directionof movement scale 52A (the Y-axis direction), and constitutes an Xlinear encoder 56A that measures the positional information of waferstage WST in the X-axis direction, together with movement scale 52A. Thepair of head units 46B₁ and 46B₂ are placed in an arrangement symmetricto an axis (center axis) parallel to the Y-axis that passes throughoptical axis AX of projection optical system PL, with the longitudinaldirection (the disposal direction of the heads) being the Y-axisdirection (the period direction of the diffraction grating), which isorthogonal to the longitudinal direction of movement scale 52B (theX-axis direction), and constitutes a Y linear encoder 56B that measuresthe positional information of wafer stage WST in the Y-axis direction attwo points, together with movement scale 52B.

Furthermore, the measurement values of the two linear encoders 56A and56B are supplied to main controller 20, and based on the positionalinformation in the X-axis and the Y-axis directions and the rotationalinformation in the θz direction, main controller 20 performs positioncontrol of wafer stage WST via wafer stage drive section 27.Accordingly, wafer stage WST can be driven two-dimensionally with highprecision, in exactly the same manner as in the embodiment above.

FIG. 26 is a view that shows a different modified example of an encodersystem for the wafer stage, and the only point different from FIG. 25besides the point that a set of linear encoders 56A and 56B was arrangedis the point that another set of linear encoders 56C and 56D isarranged. As is shown in FIG. 26, on the upper surface of wafer stageWST, two movement scales 52C and 52D whose longitudinal direction areorthogonal to each other and the longitudinal direction is the Y-axisdirection and the X-axis direction, respectively, are fixed in anL-shape. On the surface of the two movement scales 52C and 52D, areflection type diffraction grating that has a period directionorthogonal to the longitudinal direction is formed, and movement scales52C and 52D are placed in an arrangement symmetric to movement scales52A and 52B, in relation to the center of wafer stage WST.

Further, head unit 46C and a pair of head units 46D₂ and 46D₂ are eachplaced crossing the corresponding movement scales 52C and 52D, and arefixed to barrel platform 38 in a suspended state via a support member(not shown). Head unit 46C is placed symmetric to head unit 46Adescribed earlier, in relation to optical axis AX of projection opticalsystem PL (that is, arranged on the axis (center axis) parallel to theX-axis that passes through optical axis AX previously described), withthe longitudinal direction (the disposal direction of the heads) beingthe X-axis direction (the period direction of the diffraction grating),which is orthogonal to the longitudinal direction of movement scale 52C(the Y-axis direction), and constitutes an X linear encoder 56C thatmeasures the positional information of wafer stage WST in the X-axisdirection, together with movement scale 52C. The pair of head units 46D₁and 46D₂ are placed in an arrangement symmetric to head units 46B₁ and46B₂ described earlier, in relation to optical axis AX of projectionoptical system PL (that is, arranged symmetric in relation to an axis(center axis) parallel to the Y-axis that passes through optical axisAX), with the longitudinal direction (the disposal direction of theheads) being the Y-axis direction (the period direction of thediffraction grating), which is orthogonal to the longitudinal directionof movement scale 52D (the X-axis direction), and constitutes a Y linearencoder 56D that measures the positional information of wafer stage WSTin the Y-axis direction at two points, together with movement scale 52D.

Furthermore, the measurement values of the four linear encoders 56A to56D are supplied to main controller 20, and based on the positionalinformation in the X-axis and the Y-axis directions and the rotationalinformation in the θz direction, main controller 20 performs positioncontrol of wafer stage WST via wafer stage drive section 27.Accordingly, wafer stage WST can be driven two-dimensionally with highprecision, in exactly the same manner as in the embodiment above. Sincethe encoder system in FIG. 26 has four linear encoders 56A to 56D,positional information of wafer stage WST (positional information in theX-axis and the Y-axis direction and the rotational information in the θzdirection) can be constantly obtained from at least three encoders ofthe four linear encoders 56A to 56D regardless of the position of waferstage WST during wafer exposure operation, even if the head units arenot placed close to projection optical system PL when compared with theencoder system in FIG. 25. Further, in the encoder system in FIG. 26, Ylinear encoders 56B and 56D each had two head units, however, the numberof heads is not limited to this, and for example, the linear encoderscan merely have a single head unit.

Wafer X interferometer 18X₁ referred to earlier has at least onemeasurement axis that includes a measurement axis (corresponding to thesolid line in the drawings), which coincides with an axis (center axis)parallel to the X-axis that passes through optical axis AX of projectionoptical system PL. And, in the encoder system shown in FIGS. 26 and 26,X linear encoder 56A (and 56C) is placed so that the center axis (themeasurement axis in the X measurement of wafer interferometer 18X₁)coincides with the measurement axis (the disposal direction of theheads) of head unit 46A (and 46C). Further, wafer Y interferometer 18Yreferred to earlier has a plurality of measurement axes that include twomeasurement axes (corresponding to beams B4 ₁ and B4 ₂ shown by solidlines in FIGS. 25 and 26) arranged symmetric in relation to an axis(center axis) parallel to the Y-axis that passes through optical axis AXof projection optical system PL and the detection center of alignmentsystem ALG. And, Y linear encoder 56B (and 56D) is placed so that themeasurement axes (the disposal direction of the heads) of head units46B₁ and 46B₂ (and 46D₁ and 46D₂) respectively correspond to the twomeasurement axes. Accordingly, difference in measurement values becomedifficult to occur in the case the measurement axis of the linearencoder and the measurement axis of the wafer interferometer coincidewith each other as is previously described, and it becomes possible toperform the calibration operation described earlier with good precision.In the modified example, the measurement axis of the linear encoder andthe measurement axis of the wafer interferometer coincide with eachother, however, the present invention is not limited to this, and bothaxes can be placed shifted within the XY plane. Further, the same can besaid for the embodiment above (FIG. 3).

In the encoder system shown in FIGS. 25 and 26, the two or four movementscales (52A to 52D) are made of the same material (such as, for example,ceramics or low thermal expansion glass), and regarding the respectivelongitudinal directions, the length (corresponding to the width of thediffraction grating) is set longer than the size (diameter) of wafer Wso that the length covers at least the entire area of the movementstrokes (movement range) of wafer stage WST during exposure operation ofwafer W (in other words, during scanning exposure of all the shot areas,each head unit (measurement beam) does not move off the correspondingmovement scale (diffraction grating), that is, an unmeasurable state isavoided). Further, in the encoder system shown in FIGS. 25 and 26, thethree or six head units (46A to 46D₂) can each be, for example, a singlehead, or a unit having a plurality of heads that are almost seamlesslyarranged, however, in the encoder system shown in FIGS. 25 and 26, inboth cases the encoders have a plurality of heads that are placed at apredetermined distance along the longitudinal direction. Furthermore, ineach head unit, the plurality of heads are placed at a distance so thatadjacent two heads of the plurality of heads do not go astray from thecorresponding movement scale (diffraction grating), or in other words,at a distance around the same or smaller than the formation range of thediffraction gratings in the direction orthogonal to the longitudinaldirection (disposal direction of the diffraction gratings) of themovement scale. Further, the length (corresponding to the detectionrange of the diffraction gratings) of the three or six head units (46Ato 46D₂) in the longitudinal direction is set to the same level orlarger than the movement strokes of wafer stage WST so that the lengthcovers at least the entire area of the movement strokes (movement range)of wafer stage WST during exposure operation of wafer W (in other words,during scanning exposure of all the shot areas, each head unit(measurement beam) does not move off the corresponding movement scale(diffraction grating), that is, an unmeasurable state is avoided).

Further, in the exposure apparatus equipped with the encoder systemshown in FIGS. 25 and 26, calibration operation (the first to thirdcalibration operation previously described) for deciding the correctioninformation of the measurement values of each encoder is performedexactly the same as in exposure apparatus 100 (including the encodersystem shown in FIG. 3) in the embodiment above. In this case, forinstance, in each encoder, the position of the movement scale in thelongitudinal direction is set so that one end of the movement scalecoincides with the corresponding head unit, and then the movement scaleis moved in the disposal direction of the diffraction grating (thedirection orthogonal to the longitudinal direction) by a distance aroundthe same level, or more than the width of the movement scale.Furthermore, after the movement scale is moved in the longitudinaldirection by a distance around the same level as the magnitude of themeasurement beam in one head of the head units, the movement scale ismoved similarly in the disposal direction of the diffraction grating, bya distance around the same level, or more than the width of the movementscale. Hereinafter, the operation described above is repeatedlyperformed until the other end of the movement scale coincides with thehead unit. Then, based on the measurement values of the encoder obtainedby this drive and the measurement values of the wafer interferometerthat has the same measurement direction as the encoder, the correctioninformation of the encoder can be decided. In this case, wafer stage WSTwas driven so as to cover the range in the longitudinal direction whereboth ends of the movement scale coincides with the corresponding headunit, however, the present invention is not limited to this, and waferstage WST can be driven, for example, in the range in the longitudinaldirection where wafer stage WST is moved during exposure operation ofthe wafer.

In the embodiment and the modified examples described above, positioncontrol of reticle stage RST and wafer stage WST was performed usingonly the encoder system (FIGS. 2, 3, 25, and 26) previously describedduring exposure operation of the wafer. However, even if the calibrationoperation previously described (especially the short-term calibrationoperation) is performed, there may be a case when at least a part of thepositional information in the X-axis and Y-axis directions and therotational information in the θz direction necessary for the positioncontrol referred to above cannot be obtained during the exposureoperation since problems such as the position becoming unmeasurable, themeasurement accuracy exceeding an allowable range and the like occur forsome reason (such as foreign substances adhering on the movement scale,positional shift of the movement scale, tilt of the head unit or loss oftelecentricity in the head unit, displacement of the movement scale inthe Z-axis direction (the direction orthogonal to the surface) exceedingan allowable range and the like). Since the encoder system shown inFIGS. 3 and 26 have four encoders, the position control described abovecan be performed even if a problem occurs in one encoder, however, inthe encoder system shown in FIGS. 2 and 25, if a problem occurs in oneencoder, then the position control above cannot be performed.

Therefore, in the exposure apparatus, a first drive mode that uses thepositional information measured by the encoder system previouslydescribed and a second drive mode that uses the positional informationmeasured by the interferometer system previously described should beprepared, and in the setting, the first drive mode is to be usednormally during exposure operation. Then, for example, in the case whenat least a part of the positional information in the X-axis and Y-axisdirections and the rotational information in the θz direction necessaryfor the position control referred to above cannot be obtained any longerduring the exposure operation or the like, the first drive mode ispreferably switched to the second drive mode and the position control ofthe reticle stage or wafer stage is to be performed in the second drivemode. Furthermore, a third mode that uses at least a part of thepositional information measured by the encoder system previouslydescribed and at least a part of the positional information measured bythe interferometer system previously described together can also beprepared, and the position control of the reticle stage or the waferstage can be performed using one of the second and the third drivemodes, instead of using the first drive mode. The switching of the firstdrive mode to the second drive mode (or to the third drive mode) is notlimited only to the time of exposure operation, and the switching can beperformed similarly during other operations (such as for example,measurement operation as in alignment and the like). Further, in theother operations, the mode does not have to be set to the first drivemode in advance, and other drive modes (for example, one mode of thesecond and third drive modes) can be set instead of the first drivemode. In such a case, for example, when an error occurs during theposition control of the stage by the other drive mode, the mode can beswitched to a different mode (for example, the other mode of the secondand third drive modes, or the first drive mode). Furthermore, the drivemode can be made selectable during the operation other than the exposureoperation.

In the embodiment and the modified examples described above, the casehas been described where during switching operation of the positionmeasurement system, the measurement values of interferometers 18X₁ and18Y are carried over to encoders 50A to 50D after wafer stage WST issuspended for a predetermined time until the short-term variation causedby air fluctuation (temperature fluctuation of air) of the measurementvalues of interferometers 18X₁ and 18Y falls to a level that can beignored due to an averaging effect. The present invention, however, isnot limited to this, and for example, the same operation as the secondcalibration previously described can be performed and the measurementvalues of interferometers 18X₁ and 18Y can be carried over to encoders50A to 50D, based on the low order component that has been obtained inthe calibration. Further, the switching operation of the positionmeasurement system does not necessarily have to be performed. Morespecifically, the positional information of the alignment marks on waferW and the fiducial marks on wafer stage WST can be measured usingalignment system ALG and wafer interferometer system (18X₂ and 18Y), aswell as the positional information of the fiducial marks on wafer stageWST using the reticle alignment system and the encoder system, and basedon the positional information, position control of the wafer stage canbe performed by the encoder system.

Further, in the embodiment and the modified examples described above,the case has been described where the system was switched from theinterferometer to the encoder as the switching operation of the positionmeasurement system, however, the present invention is not limited tothis. For example, in the case such as when alignment system ALG isinstalled at a position sufficiently away from projection unit PU, headunits similar to head units 46A to 46D should be arranged in the areawhere the alignment operation using alignment system ALG is to beperformed, in the shape of a cross with alignment system ALG in thecenter. Then, an origin is set for each of the movement scales 44A to44D, and on wafer alignment such as EGA, the positional information ofeach alignment mark on wafer W that uses an origin of a coordinatesystem set by the combination of movement scales 44A to 44D as areference is detected using the head units and movement scales 44A to44D, and then, based on the detection results, a predeterminedcalculation can be performed so as to obtain relative positionalinformation of each shot area with respect to the origin referred toabove. In this case, on exposure, by detecting the origin using encoders50A to 50D, each shot area can be moved to the acceleration startingposition for exposure using the relative positional information of eachshot area with respect to the origin referred to above. In this case,since position drift between the head and projection unit PU/alignmentsystem ALG also becomes an error cause, it is preferable to performcalibration on the positional shift.

In the embodiment and the modified examples described above, positioncontrol of reticle stage RST and wafer stage WST was performed duringexposure operation of the wafer using the encoder system previouslydescribed (FIGS. 2, 3, 25, and 26), however the position control of thestages using the encoder system is not limited only during exposureoperation, and besides during the exposure operation, for example, inthe detection operation of the reticle alignment marks or the referencemarks on reticle stage RST using the reticle alignment system, or in thereticle exchange operation, position control of reticle stage RST can beperformed using the encoder system shown in FIG. 2. Similarly, forexample, in the detection operation of the alignment marks of wafer Wusing alignment system ALG, or in the wafer exchange operation, positioncontrol of wafer stage WST can be performed using the encoder systemshown in FIGS. 3, 25, and 26. In this case, as a matter of course, theswitching operation of the position measurement system will not berequired.

In the case of using the encoder system previously described (FIGS. 3,25, and 26), during the detection of the alignment marks on wafer W orfiducial marks on wafer stage WST using alignment system ALG, or duringthe detection of the fiducial marks on wafer stage WST using the reticlealignment system, it is preferable to take into consideration themovement range of wafer stage WST during the detection operation. It ispreferable to set the length (or placement) in the longitudinaldirection of each of the head units or to arrange head units differentfrom each of the head units above, so that especially during the markdetection operation performed when the wafer stage is moved to themeasurement position of alignment system ALG, each of the head units(46A to 46D, 46A to 46D₂) does not move away from the correspondingmeasurement scales (diffraction gratings), that is, the situation wherethe measurement using the encoder system becomes unmeasurable and theposition control of the wafer stage is cut off is avoided.

Further, in the case of using the encoder system previously described(FIGS. 3, 25, and 26) at the wafer exchange position (including at leastone of the loading position and the unloading position), or during themovement from one point to the other between the wafer exchange positionand the exposure position where transfer of the reticle pattern isperformed via projection optical system PL or to the measurementposition where mark detection by alignment system ALG is performed, itis preferable to similarly take into consideration the movement range ofwafer stage WST at the wafer exchange position and during wafer exchangeoperation, and to set the placement and the length each of the headunits or to arrange head units different from each of the head unitsabove, so that the situation where the measurement using the encodersystem becomes unmeasurable and the position control of the wafer stageis cut off is avoided.

Furthermore, even in an exposure apparatus by the twin wafer stagemethod that can perform exposure operation and measurement operationsubstantially in parallel using two wafer stages whose details aredisclosed in, for example, Kokai (Japanese Unexamined PatentPublication) No. 10-214783 and the corresponding U.S. Pat. No.6,341,007, and in the pamphlet of International Publication WO98/40791and the corresponding U.S. Pat. No. 6,262,796 and the like, positioncontrol of each wafer stage can be performed using the encoder systempreviously described (FIGS. 3, 25, and 26). In this case, byappropriately setting the placement and the length each of the headunits not only during exposure operation but also during measurementoperation, it becomes possible to perform position control of each waferstage using the encoder system previously described (FIGS. 3, 25, and26) without any changes. However, head units that can be used during themeasurement operation separate from the head units previously described(46A to 46D, and 54A to 54D₂) can also be arranged. For example, fourhead units can be arranged in the shape of a cross with alignment systemALG in the center, and during the measurement operation above,positional information of each wafer stage WST can be measured usingthese units and the corresponding movement scales (46A to 46D, and 52Ato 52D). In the exposure apparatus by the twin wafer stage method, twoor four movement scales (FIGS. 3, 25, and 26) are arranged, and whenexposure operation of a wafer mounted on one of the stages is completed,then the wafer stage is exchanged so that the other wafer stage on whichthe next wafer that has undergone mark detection and the like at themeasurement position is placed at the exposure position. Further, themeasurement operation performed in parallel with the exposure operationis not limited to mark detection of the wafer by the alignment system,and instead of, or in combination with the mark detection, for example,detection of the surface information (level difference information) ofthe wafer can also be performed.

In the description above, when the position control of the wafer stageusing the encoder system is cut off at the measurement position orexchange position, or while the wafer stage is moved from one of theexposure position, measurement position, and exchange position toanother position, it is preferable to perform position control of thewafer stage at each of the positions above or during the movement usinganother measurement unit (e.g. an interferometer or an encoder) separatefrom the encoder system.

Further, in the embodiment and the modified examples described above, asis disclosed in, for example, the pamphlet of International PublicationWO2005/074014, the pamphlet of International Publication WO1999/23692,U.S. Pat. No. 6,897,963 and the like, a measurement stage that has ameasurement member (a reference mark, a sensor and the like) can bearranged separate from the wafer stage, and during wafer exchangeoperation or the like, the measurement stage can be exchanged with thewafer stage and be placed directly under projection optical system PL soas to measure the characteristics of the exposure apparatus (e.g. theimage-forming characteristics of the projection optical system (such aswavefront aberration), polarization characteristics of illuminationlight IL, and the like). In this case, movement scales can also beplaced on the measurement stage, and the position control of themeasurement stage can be performed using the encoder system previouslydescribed. Further, during the exposure operation of the wafer mountedon the wafer stage, the measurement stage is withdrawn to apredetermined position where it does not interfere with the wafer stage,and the measurement stage is to move between this withdrawal positionand the exposure position. Therefore, at the withdrawal position orduring the movement from one position to the other between thewithdrawal position and the exposure position, it is preferable to takeinto consideration the movement range of the measurement stage as in thecase of the wafer stage, and to set the placement and the length each ofthe head units or to arrange head units different from each of the headunits above, so that the situation where the measurement using theencoder system becomes unmeasurable and the position control of themeasurement stage is cut off is avoided. Or, when the position controlof the measurement stage by the encoder system is cut off at thewithdrawal position or during the movement, it is preferable to performposition control of the measurement stage using another measurement unit(e.g. an interferometer or an encoder) separate from the encoder system.

Further, in the embodiment and the modified examples described above,for example, depending on the size of projection unit PU, the distancebetween the pair of head units arranged extending in the same directionhas to be increased, which could cause one unit of the pair of headunits to move away from the corresponding movement scale during thescanning exposure of a specific shot area on wafer W, such as, forexample, a shot area located on the outermost periphery. For instance,when projection unit PU becomes a little larger in FIG. 3, of the pairof head units 46B and 46D, head unit 46B may move away from thecorresponding movement scale 44B. Furthermore, in a liquid immersiontype exposure apparatus that has liquid (e.g. pure water or the like)filled in the space between projection optical system PL and the waferwhose details are disclosed in, for example, the pamphlet ofInternational Publication WO99/49504, the pamphlet of InternationalPublication WO2004/053955 (the corresponding U.S. Patent ApplicationPublication 2005/0252506), U.S. Pat. No. 6,952,253, European PatentApplication Publication No. 1420298, the pamphlet of InternationalPublication WO2004/055803, the pamphlet of International PublicationWO2004/057590, U.S. Patent Application Publication 2006/0231206, U.S.Patent Application Publication 2005/0280791 and the like, since a nozzlemember for supplying the liquid is arranged surrounding projection unitPU, it becomes more difficult to place the head units close to theexposure area previously described of projection optical system PL.Therefore, in the encoder system shown in FIGS. 3 and 26, the twopositional information each for both the X-axis and Y-axis directionsdoes not necessarily have to be measurable at all times, and the encodersystem (especially the head unit) can be configured so that twopositional information is measurable in one of the X-axis and Y-axisdirections and one positional information is measurable in the other ofthe X-axis and Y-axis directions. That is, in the position control ofthe wafer stage (or the measurement stage) by the encoder system, thetwo positional information each for both the X-axis and Y-axisdirections, which is a total of four positional information, does notnecessarily have to be used. Further, in the liquid immersion exposureapparatus, as is shown in FIG. 27, for example, a liquid repellent plateWRP on the upper surface of wafer stage WST (or wafer table WTB) can bemade of glass, and the scale pattern can be arranged directly on theglass. Or, the wafer table can be made of glass. In the liquid immersionexposure apparatus equipped with a wafer stage (or a measurement stage)that has the movement scales in the embodiment and the modified examplesdescribed above (FIGS. 3, 25, and 26), it is preferable to form a liquidrepellent film on the surface of the movement scales.

When taking into consideration the decrease in size and weight of waferstage WST, it is preferable to place the movement scales as close aspossible to wafer W on wafer stage WST. However, when increasing thesize of the wafer stage is acceptable, by increasing the size of thewafer stage as well as the distance of the pair of movement scalesplaced facing each other, the two positional information each for boththe X-axis and Y-axis directions, which is a total of four positionalinformation, can be constantly measured at least during the exposureoperation of the wafer. Further, instead of increasing the size of thewafer stage, for example, the movement scale can be arranged on thewafer stage so that a part of the movement scale protrudes from thewafer stage, or the movement scale can be placed on the outer side ofthe wafer stage main section using an auxiliary plate on which at leastone movement scales is arranged so as to increase the distance of thepair of movement scales placed facing each other.

Further, prior to performing the position control of the stage by theencoder system, for example, it is preferable to measure the tilt of thehead units (tilt with respect to the Z-axis direction), disposal of theheads within the XY plane (the position, distance or the like), tilt oftelecentricity of the heads, and the like, and to use the measurementresults in the position control described above. Furthermore, forexample, it is preferable to measure the displacement amount, thegradient amount or the like of the movement scale in the Z-axisdirection (the direction perpendicular to the surface), and to use themeasurement results in the position control described above.

The first to third calibration operation and the sequential calibrationoperation described in the embodiment and the modified examples abovecan be performed separately, or appropriately combined. Further, duringthe position measurement by the encoder system and the interferometersystem in the calibration operation, the stage was moved at a low speed,however, the present invention is not limited to this, and the stage canbe moved at the same level of speed as during the scanning exposurepreviously described.

Further, in the embodiment and the modified examples above, positioncontrol of the reticle stage and wafer stage was performed using theencoder system. The present invention, however, is not limited to this,and for example, position control using the encoder system can beperformed in one of the reticle stage and the wafer stage, and in theother stage, position control using the interferometer system can beperformed. Furthermore, in the in the embodiment and the modifiedexamples above, the head units of the encoders were placed above thereticle stage, however, the head units of the encoders can be placedbelow the reticle stage. In this case, the movement scale is also to bearranged on the lower surface side of the reticle stage.

Furthermore, in the encoder system of the embodiment and the modifiedexamples above (FIGS. 3, 25, and 26), the plurality of movement scales(44A to 44D, and 52A to 52D) are each fixed to wafer stage WST, forexample, by a suction mechanism such as a vacuum chuck or a platespring, however, the movement scales can also be fixed, for example, bya screw clamp, or the diffraction grating can be formed directly on thewafer stage. Especially in the latter case, the diffraction grating canbe formed on the table where the wafer holder is formed, or especiallyin the liquid immersion exposure apparatus, the diffraction grating canbe formed on the liquid repellent plate. Further, in both reticle stageRST and wafer stage WST, the member on which the diffraction grating isformed (including the measurement scale or the like described earlier)is preferably configured of a low thermal expansion material such asceramics (e.g. Zerodur of Schott Corporation or the like). Further, inorder to prevent the measurement accuracy from decreasing due to foreignsubstances adhesion or contamination, for example, at least a coatingcan be applied to the surface so as to cover the diffraction grating, ora cover glass can be arranged. Furthermore, in both reticle stage RSTand wafer stage WST, the diffraction grating was continuously formedsubstantially covering the entire surface of each movement scale in thelongitudinal direction, however, for example, the diffraction gratingcan be formed intermittently, divided into a plurality of areas, or eachmovement scale can be made up of a plurality of scales.

In the encoder system of the embodiment and the modified examples above,especially in the encoder system in FIG. 3, the case was exemplifiedwhere the pair of movement scales 44A and 44C used for measuring theposition in the Y-axis direction and the pair of movement scales 44B and44D used for measuring the position in the X-axis direction are arrangedon wafer stage WST, and corresponding to the movement scales, the pairof head units 46A and 46C is arranged on one side and the other side inthe X-axis direction of projection optical system PL and the pair headunits 46B and 46D is arranged on one side and the other side in theY-axis direction of projection optical system PL. However, the presentinvention is not limited to this, and of movement scales 44A and 44Cused for measuring the position in the Y-axis direction and movementscales 44B and 44D used for measuring the position in the X-axisdirection, at least one set of the movement scales can be a single unitinstead of in pairs arranged on wafer stage WST, or of the pair of headunits 46A and 46C and the pair head units 46B and 46D, at least one setof the head units can be a single unit arranged instead of in pairs. Thesame can be said for the encoder system shown in FIG. 26. Further, theextending direction in which the movement scales are arranged and theextending direction in which the head units are arranged are not limitedto an orthogonal direction as in the X-axis direction and Y-axisdirection in the embodiment above.

Further, in the embodiment and the modified examples above, theconfiguration of wafer interferometer system 18 is not limited to theone shown in FIG. 3, and for example, in the case of placing a head unitalso in alignment system ALG (measurement position), the interferometersystem does not have to be equipped with wafer X interferometer 18X₂, orwafer X interferometer 18X₂ can be configured, for example, by amulti-axis interferometer as in wafer Y interferometer 18Y, and besidesthe X position of wafer stage WST, rotational information (such asyawing and rolling) can be measured. Further, similar to wafer Xinterferometer 18X₁, wafer Y interferometer 18Y can be a single-axisinterferometer, and wafer X interferometer 18X₁ can be a multi-axisinterferometer similar to wafer Y interferometer 18Y. The multi-axisinterferometer can be configured so that only yawing is measurable asthe rotational information. Furthermore, in one of wafer Xinterferometer 18X₁ and wafer Y interferometer 18Y, the interferometercan be configured so that the rotational information measurable islimited to one (rolling or pitching). That is, wafer interferometersystem 18 of the embodiment can employ various configurations as long asat least the positional information in the X-axis and Y-axis directionand the rotational information in the θz direction (yawing) can bemeasured during the exposure operation of the wafer.

In the embodiment above, the case has been described where the presentinvention was applied to a scanning stepper. The present invention,however, is not limited to this, and it can be applied to a staticexposure apparatus such as a stepper. Even in the case of a stepper, bymeasuring the position of the stage on which the object subject toexposure is mounted using an encoder, generation of position measurementerrors due to air fluctuation can be reduced almost to zero, unlike whenthe position of the stage is measured using the interferometer. Further,based on correction information for correcting the short-term variationof the measurement values of the encoder using the measurement values ofthe interferometer and on the measurement values of the encoder, itbecomes possible to set the position of the stage with high precision,which makes it possible to transfer the reticle pattern onto the objectwith high precision. Further, the present invention can also be appliedto a reduction projection exposure apparatus by the step-and-stitchmethod that merges shot areas, an exposure apparatus by a proximitymethod, a mirror projection aligner or the like.

Further, the magnification of the projection optical system in theexposure apparatus of the embodiment above is not limited to a reductionsystem, and the system may be either an equal magnifying system or amagnifying system. Projection optical system PL is not limited to arefracting system, and the system can be either a reflection system or acatadioptric system, and the projected image can be either an invertedimage or an upright image. Furthermore, the exposure area on whichillumination light IL is irradiated via projection optical system PL isan on-axis area including optical axis AX within the field of view ofprojection optical system PL, however, the exposure area can be anoff-axis area that does not include optical axis AX similar to theso-called inline type catodioptric system, which has an optical system(a reflection system or a deflexion system) that has a plurality ofreflection surfaces and forms an intermediate image at least oncearranged in a part of the catodioptric system and also has a singleoptical axis, disclosed in, for example, the pamphlet of InternationalPublication WO2004/107011. Further, the shape of the illumination areaand the exposure area previously described was a rectangle, however, theshape is not limited to this, and it can be, for example, a circulararc, a trapezoid, a parallelogram or the like.

Further, illumination light IL is not limited to the ArF excimer laserbeam (wavelength 193 nm), and illumination light IL can be anultraviolet light such as the KrF excimer laser beam (wavelength 248 nm)or the like, or a vacuum ultraviolet light such as the F₂ laser beam(wavelength 157 nm). As a vacuum ultraviolet light, as is disclosed in,for example, the pamphlet of International Publication WO1999/46835 (thecorresponding U.S. Pat. No. 7,023,610), a harmonic wave may also be usedthat is obtained by amplifying a single-wavelength laser beam in theinfrared or visible range emitted by a DFB semiconductor laser or fiberlaser, with a fiber amplifier doped with, for example, erbium (or botherbium and ytteribium), and by converting the wavelength intoultraviolet light using a nonlinear optical crystal.

Further, in the embodiment above, it is a matter of course that asillumination light IL of the exposure apparatus the light is not limitedto a light that has a wavelength of 100 nm or more, and a light whosewavelength is less than 100 nm can also be used. For example, in recentyears, in order to expose a pattern of 70 nm or under, an EUV exposureapparatus is being developed that generates an EUV (Extreme Ultraviolet)light in the soft X-ray region (e.g. wavelength range of 5 to 15 nm)using an SOR or a plasma laser as a light source and uses an allreflection reduction optical system, which is designed based on theexposure wavelength (e.g. 13.5 nm), and a reflection typed mask. In thisapparatus, because the structure of scanning exposure in which the maskand the wafer are synchronously scanned using a circular arcillumination can be considered, the present invention can also besuitably applied to the apparatus. Besides such apparatus, the presentinvention can also be applied to an exposure apparatus that uses acharged particle beam such as an electron beam or an ion beam.

Further, in the embodiment described above, a transmittance type mask(reticle) was used, which is a transmissive substrate on which apredetermined light shielding pattern (or a phase pattern or a lightattenuation pattern) is formed. Instead of this mask, however, as isdisclosed in, for example, U.S. Pat. No. 6,778,257, an electron mask(also called a variable shaped mask, an active mask, or an imagegenerator, and includes, for example, a DMD (Digital MicromirrorDevice), which is a kind of a non-radiative image display device (alsoreferred to as a spatial optical modulator), or the like) on which alight-transmitting pattern, a reflection pattern, or an emission patternis formed according to electronic data of the pattern that should beexposed can also be used. In the case of using such a variable shapedmask, because the stage on which the wafer, the glass plate or the likeis mounted is scanned with respect to the variable shaped mask, bymeasuring the position of the stage using the encoder and performingcalibration on the measurement values of the encoder using themeasurement values of the interferometer as is previously described, thesame effect as in the embodiment above can be obtained.

Further, for example, as is disclosed in, the pamphlet of InternationalPublication WO2001/035168, by forming interference fringes on wafer W,the present invention can also be applied to an exposure apparatus (alithography system) that forms a line-and-space pattern on wafer W.

Furthermore, as is disclosed in, for example, Kohyo (Japanese UnexaminedPatent Publication) No. 2004-519850 (the corresponding U.S. Pat. No.6,611,316), the present invention can also be applied to an exposureapparatus that synthesizes patterns of two reticles on a wafer via adouble-barrel projection optical system, and performs double exposure ofa shot area on the wafer almost simultaneously in one scanning exposure.

Further, the apparatus for forming a pattern on an object is not limitedto the exposure apparatus (lithography system) previously described, andfor example, the present invention can also be applied to an apparatusfor forming a pattern on an object by an inkjet method.

The object on which the pattern is to be formed in the embodiment above(the object subject to exposure on which the energy beam is irradiated)is not limited to a wafer, and can be other objects such as, a glassplate, a ceramic substrate, a mask blank, a film member or the like.Further, the shape of the object is not limited to a circular shape, andit can be other shapes such as a rectangular shape or the like.

The usage of the exposure apparatus is not limited to the exposureapparatus for manufacturing semiconductors, and the present inventioncan also be widely applied to an exposure apparatus for liquid crystalsthat transfers a liquid crystal display device pattern on a square glassplate or the like, or to an exposure apparatus used for manufacturingorganic ELs, thin film magnetic heads, imaging devices (such as CCDs),micromachines, DNA chips and the like. Further, the present inventioncan also be applied to an exposure apparatus that transfers a circuitpattern onto a glass substrate or a silicon wafer not only whenproducing microdevices such as semiconductors, but also when producing areticle or a mask used in exposure apparatus such as an optical exposureapparatus, an EUV exposure apparatus, an X-ray exposure apparatus, anelectron beam exposure apparatus and the like.

The present invention is not limited to an exposure apparatus, and canalso be widely applied to other substrate processing units (e.g. a laserrepair unit, a substrate inspection unit and the like), or to anapparatus equipped with a movement stage of a position setting unit of asample, a wire bonding unit and the like in other precision machinery.

The disclosures of all the publications, the pamphlet of theInternational Publications, the U.S. Patent Application Publication, andthe U.S. Patent descriptions related to the exposure apparatus or thelike referred to above are each incorporated herein by reference.

Semiconductor devices are manufactured through the following steps: astep where the function/performance design of a device is performed; astep where a reticle based on the design step is manufactured; a stepwhere a wafer is manufactured using materials such as silicon; alithography step where the pattern formed on the mask is transferredonto a photosensitive object using the exposure apparatus described inthe embodiment above; a device assembly step (including processes suchas a dicing process, a bonding process, and a packaging process); aninspection step, and the like. In this case, in the lithography step,because the exposure apparatus in the embodiment above is used, highintegration devices can be manufactured with good yield.

The exposure apparatus in the embodiment and the modified examples abovecan be made by assembling various subsystems that include each of thecomponents given in the scope of the claims of the present applicationso that a predetermined mechanical accuracy, electrical accuracy, andoptical accuracy are maintained. In order to secure these variousaccuracies, before and after the assembly, adjustment for achieving theoptical accuracy is performed for the various optical systems,adjustment for achieving the mechanical accuracy is performed for thevarious mechanical systems, and adjustment for achieving the electricalaccuracy is performed for the various electric systems. The assemblyprocess from the various subsystems to the exposure apparatus includesmechanical connection, wiring connection of the electric circuits,piping connection of the pressure circuits and the like between thevarious subsystems. It is a matter of course that prior to the assemblyprocess from the various subsystems to the exposure apparatus, there isan assembly process for each of the individual subsystems. When theassembly process from the various subsystems to the exposure apparatushas been completed, total adjustment is performed, and the variousaccuracies in the exposure apparatus as a whole are secured. Theexposure apparatus is preferably built in a clean room where conditionssuch as the temperature and the degree of cleanliness are controlled.

While the above-described embodiments of the present invention are thepresently preferred embodiments thereof, those skilled in the art oflithography systems will readily recognize that numerous additions,modifications, and substitutions may be made to the above-describedembodiments without departing from the spirit and scope thereof. It isintended that all such modifications, additions, and substitutions fallwithin the scope of the present invention, which is best defined by theclaims appended below.

What is claimed is:
 1. An exposure apparatus that has an illuminationoptical system to illuminate a mask with an illumination light and aprojection optical system to project a pattern image of the illuminatedmask onto a substrate, the apparatus comprising: a mask stage systemhaving a first stage and a first motor, the first stage being disposedabove the projection optical system and configured to hold the mask, andthe first motor driving the first stage; a first encoder system in whichone of a first head and a first scale member is provided at the firststage, and which irradiates a reflection type grating of the first scalemember with a first measurement beam via the first head and measurespositional information of the first stage with a plurality of the firstheads that face the first scale member; a substrate stage system havinga second stage and a second motor, the second stage being disposed belowthe projection optical system and configured to hold the substrate, andthe second motor driving the second stage; a second encoder system thatirradiates a second scale member having four grating sections with asecond measurement beam via a second head, and measures positionalinformation of the second stage with a plurality of the second headsthat face the second scale member, each of the four grating sectionshaving a reflection type grating that is disposed substantially parallelto a predetermined plane orthogonal to an optical axis of the projectionoptical system; and a controller coupled to the mask stage system andthe substrate stage system, the controller controlling the first motorand the second motor based on measurement information of the firstencoder system and measurement information of the second encoder system,respectively, wherein in an exposure operation of the substrate, thecontroller moves the first and the second stages so that a plurality ofareas of the substrate are exposed by scanning exposure in which themask and the substrate are each moved relative to the illuminationlight, at least in the exposure operation, a relationship between thesecond heads and the second scale member is changed from one of a firststate and a second state to the other of the first state and the secondstate so that the number of the second heads that face the second scalemember is changed according to movement of the second stage in adirection parallel to the predetermined plane, wherein in the firststate, four of the second heads face the four grating sections,respectively, and in the second state, three of the second heads facethree grating sections of the four grating sections, respectively, andnone of the second heads faces another grating section that is differentfrom the three grating sections, of the four grating sections, and atleast during the scanning exposure, at least three of the second headsface at least three of the four grating sections, respectively.
 2. Theexposure apparatus according to claim 1, wherein one of the plurality ofsecond heads that face the second scale member is switched to anothersecond head, according to movement of the second stage in the directionparallel to the predetermined plane, the another second head beingdifferent from the plurality of second heads, and after the switching,the positional information of the second stage is measured with aplurality of second heads, including the another second head, that facethe second scale member.
 3. The exposure apparatus according to claim 2,further comprising: a second detection system that is disposed spacedfrom the projection optical system and detects a mark of the substrateand a mark of the second stage, wherein in each of the exposureoperation and a detection operation of the marks, the positionalinformation of the second stage is measured with the second encodersystem.
 4. The exposure apparatus according to claim 3, wherein thesubstrate stage system has a plurality of second stages including thesecond stage, each of the plurality of second stages being configured tohold a substrate, and the second encoder system measures positionalinformation of the plurality of second stages.
 5. The exposure apparatusaccording to claim 3, wherein in the scanning exposure, the controllermoves the first stage so that the mask is moved relative to theillumination light in a first direction within the predetermined plane,and the plurality of first heads include at least one first head that isswitched from one of a state and another state to the other of the stateand the another state according to movement of the first stage in thefirst direction, in the state the first measurement beam beingirradiated on the reflection type grating, and in the another state thefirst measurement beam moving off from the reflection type grating. 6.The exposure apparatus according to claim 5, wherein in a differentoperation that is different from the scanning exposure, the positionalinformation of the first stage is measured with the at least one firsthead, and the different operation includes an exchange operation of amask held by the first stage, the exchange operation being performed ata position spaced from an illumination area of the mask in the firstdirection, the illumination area being irradiated with the illuminationlight.
 7. The exposure apparatus according to claim 6, wherein duringthe scanning exposure, the positional information of the first stage ismeasured with at least two first heads that are different from the atleast one first head, of the plurality of first heads, and the at leastone first head is disposed farther from the illumination area than theat least two first heads in the first direction.
 8. The exposureapparatus according to claim 5, wherein the plurality of first headsinclude at least two first heads that are disposed spaced from eachother in a second direction that is orthogonal to the first directionwithin the predetermined plane, and during the scanning exposure, thepositional information of the first stage is measured with the at leasttwo first heads.
 9. The exposure apparatus according to claim 8, whereinthe first scale member has two grating sections that are disposed onboth sides of an illumination area of the mask in the second direction,the illumination area being irradiated with the illumination light, andthe at least two first heads include two first heads that irradiate thetwo grating sections of the first scale member, respectively, with thefirst measurement beam.
 10. The exposure apparatus according to claim 9,wherein the at least two first heads include another first head that isdifferent from the two first heads, of the plurality of first heads, andthe another first head is different in position in the first directionfrom at least one of the two first heads.
 11. The exposure apparatusaccording to claim 9, wherein the at least two first heads include theat least one first head, and in the at least one first head, the firstmeasurement beam moves off from the reflection type grating in a perioddifferent from the scanning exposure.
 12. The exposure apparatusaccording to claim 9, further comprising: a first detection system thatdetects a mark of the mask or a mark of the first stage via theprojection optical system, the first detection system being differentform the second detection system, wherein in each of the exposureoperation and a detection operation of the mark by the first detectionsystem, the positional information of the first stage is measured withthe first encoder system.
 13. The exposure apparatus according to claim12, further comprising: a body that has a frame member, the frame membersupporting the projection optical system, wherein the other of the firstheads and the first scale member is provided at the body.
 14. A devicemanufacturing method, including: a lithography process of transferring apattern onto a substrate using the exposure apparatus according toclaim
 1. 15. An exposure method of illuminating a mask with anillumination light via an illumination optical system and exposing asubstrate with the illumination light via a projection optical system,the method comprising: moving the mask with a mask stage system having afirst stage and a first motor, the first stage being disposed above theprojection optical system and holding the mask, and the first motordriving the first stage; in a first encoder system in which one of afirst head and a first scale member is provided at the first stage, andwhich irradiates a reflection type grating of the first scale memberwith a first measurement beam via the first head, measuring positionalinformation of the first stage with a plurality of the first heads thatface the first scale member; moving the substrate with a substrate stagesystem having a second stage and a second motor, the second stage beingdisposed below the projection optical system and holding the substrate,and the second motor driving the second stage; in a second encodersystem that irradiates a second scale member having four gratingsections with a second measurement beam via a second head, measuringpositional information of the second stage with a plurality of thesecond heads that face the second scale member, each of the four gratingsections having a reflection type grating that is disposed substantiallyparallel to a predetermined plane orthogonal to an optical axis of theprojection optical system; and controlling the first motor and thesecond motor based on measurement information of the first encodersystem and measurement information of the second encoder system,respectively, wherein in an exposure operation of the substrate, aplurality of areas of the substrate are exposed by scanning exposure inwhich the mask and the substrate are each moved relative to theillumination light, at least in the exposure operation, a relationshipbetween the second heads and the second scale member is changed from oneof a first state and a second state to the other of the first state andthe second state so that the number of the second heads that face thesecond scale member is changed according to movement of the second stagein a direction parallel to the predetermined plane, wherein in the firststate, four of the second heads face the four grating sections,respectively, and in the second state, three of the second heads facethree grating sections of the four grating sections, respectively, andnone of the second heads faces another grating section that is differentfrom the three grating sections, of the four grating sections, and atleast during the scanning exposure, at least three of the second headsface at least three of the four grating sections, respectively.
 16. Theexposure method according to claim 15, wherein one of the plurality ofsecond heads that face the second scale member is switched to anothersecond head, according to movement of the second stage in the directionparallel to the predetermined plane, the another second head beingdifferent from the plurality of second heads, and after the switching,the positional information of the second stage is measured with aplurality of second heads, including the another second head, that facethe second scale member.
 17. The exposure method according to claim 16,wherein a mark of the substrate and a mark of the second stage aredetected with a second detection system that is disposed spaced from theprojection optical system, and in each of the exposure operation and adetection operation of the marks, the positional information of thesecond stage is measured with the second encoder system.
 18. Theexposure method according to claim 17, wherein in the scanning exposure,the mask is moved relative to the illumination light in a firstdirection within the predetermined plane, and the plurality of firstheads include at least one first head that is switched from one of astate and another state to the other of the state and the another stateaccording to movement of the first stage in the first direction, in thestate the first measurement beam being irradiated on the reflection typegrating, and in the another state the first measurement beam moving offfrom the reflection type grating.
 19. The exposure method according toclaim 18, wherein in a different operation that is different from thescanning exposure, the positional information of the first stage ismeasured with the at least one first head, and the different operationincludes an exchange operation of a mask held by the first stage, theexchange operation being performed at a position spaced from anillumination area of the mask in the first direction, the illuminationarea being irradiated with the illumination light.
 20. The exposuremethod according to claim 19, wherein during the scanning exposure, thepositional information of the first stage is measured with at least twofirst heads that are different from the at least one first head, of theplurality of first heads, and the at least one first head is disposedfarther from the illumination area than the at least two first heads inthe first direction.
 21. The exposure method according to claim 18,wherein during the scanning exposure, the positional information of thefirst stage is measured with at least two first heads, of the pluralityof first heads, that are disposed spaced from each other in a seconddirection that is orthogonal to the first direction within thepredetermined plane.
 22. The exposure method according to claim 21,wherein the first scale member has two grating sections that aredisposed on both sides of an illumination area of the mask in the seconddirection, the illumination area being irradiated with the illuminationlight, and the at least two first heads include two first heads thatirradiate the two grating sections of the first scale member,respectively, with the first measurement beam.
 23. The exposure methodaccording to claim 22, wherein the at least two first heads includeanother first head that is different from the two first heads, of theplurality of first heads, and the another first head is different inposition in the first direction from at least one of the two firstheads.
 24. The exposure method according to claim 22, wherein the atleast two first heads include the at least one first head, and in the atleast one first head, the first measurement beam moves off from thereflection type grating in a period different from the scanningexposure.
 25. The exposure method according to claim 22, wherein a markof the mask or a mark of the first stage is detected with a firstdetection system via the projection optical system, the first detectionsystem being different form the second detection system, and in each ofthe exposure operation and a detection operation of the mark by thefirst detection system, the positional information of the first stage ismeasured with the first encoder system.
 26. A device manufacturingmethod, including: a lithography process of transferring a pattern ontoa substrate using the exposure method according to claim
 15. 27. Amaking method of an exposure apparatus that has an illumination opticalsystem to illuminate a mask with an illumination light and a projectionoptical system to project a pattern image of the illuminated mask onto asubstrate, the method comprising: providing a mask stage system having afirst stage and a first motor, the first stage being disposed above theprojection optical system and configured to hold the mask, and the firstmotor driving the first stage; providing a first encoder system in whichone of a first head and a first scale member is provided at the firststage, and which irradiates a reflection type grating of the first scalemember with a first measurement beam via the first head and measurespositional information of the first stage with a plurality of the firstheads that face the first scale member; providing a substrate stagesystem having a second stage and a second motor, the second stage beingdisposed below the projection optical system and configured to hold thesubstrate, and the second motor driving the second stage; providing asecond encoder system that irradiates a second scale member having fourgrating sections with a second measurement beam via a second head, andmeasures positional information of the second stage with a plurality ofthe second heads that face the second scale member, each of the fourgrating sections having a reflection type grating that is disposedsubstantially parallel to a predetermined plane orthogonal to an opticalaxis of the projection optical system; and providing a controllercoupled to the mask stage system and the substrate stage system, thecontroller controlling the first motor and the second motor based onmeasurement information of the first encoder system and measurementinformation of the second encoder system, respectively, wherein in anexposure operation of the substrate, the controller moves the first andthe second stages so that a plurality of areas of the substrate areexposed by scanning exposure in which the mask and the substrate areeach moved relative to the illumination light, at least in the exposureoperation, a relationship between the second heads and the second scalemember is changed from one of a first state and a second state to theother of the first state and the second state so that the number of thesecond heads that face the second scale member is changed according tomovement of the second stage in a direction parallel to thepredetermined plane, wherein in the first state, four of the secondheads face the four grating sections, respectively, and in the secondstate, three of the second heads face three grating sections of the fourgrating sections, respectively, and none of the second heads facesanother grating section that is different from the three gratingsections, of the four grating sections, and at least during the scanningexposure, at least three of the second heads face at least three of thefour grating sections, respectively.